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TRIV4SIT NOIRE AND VTBRATION It'1PACT ASSESSMENT r1ANUAL A plan to use wayside horns in place of the locomotive horn at public grade crossings must he coordl robed with several public and private entities, notably the local agency having responsibility for traffic control and law enforcement on the road crossings, the state agency responsible for railroad safety. any railroads that share the ROW, and FRA Public notification must aka be glvert Preliminary cast information fragn tftting programs Indicates a wayside horn system at a rail?roadrhighway grade crossing costs approximately $50,000.
• Buffer Zones — Rouse noise levels attenuate with distance, one noise rnitigatian option Is to increase the distance berweei noise sources and rho clmint noise -sensitive receivers. This can be accomplished by locating alignments away from noise -sensitive sites. Acquisition of land or purchasing easements for noise buffer zones is an option that may be ceursidered if appropriate far the prokect.
▪ Ground Absorption — Ballast on Guideways — Propagation of noise over ground is affected by whether the ground surface is absorptive or reflective_ Noise from vehicles on the surface is strongly affected by the character of the ground rn the immediate vicinity of the vehicle. Roads and sir°sets fear buses are hard and reflective, but the ground at the side of a road hasa substantial effect on the propagation of noise to greater distance.
Guideways for rail systems son be either reflective or absorptive, depending an whether they are concrete or balF≥r_ Ballast on a guideway can reduce train noise 3 dB at -grade and up to 5 dB can an aerial structure. • Vegetation and Trees — In almost all cases, vegtration arsd trees are ineffective at providing noise mitigation. Vegetation and Try can provide some mitigation if at least l t ft of trees Intervene between this source and re€,eiver, if no mar line — al —sight exists be=tween the source and receiver, and if the trees extend I5 ft or more above the line -of -sight as dezoilaed in Section 4.5. Step 3b. This is generally not a recommended form of mitigation to pu-sue_
Tt- Evaluate Receiver Treatments — Consider treatments to the receivers when noise mitig-ation treatments cannot be applied at the source or along the propagation path, or if combinations of treatments are required_ Common receiver treatments and their es 11 mated acountic- I effectiveness are Included in Table 4-35 and are described in this section.
T able 4-35 Transit Nolte Mitigation Meaturres — Receiver Treattx,ents Mitigation Measure
E Ivsness
Acgii sitien of Property Rights for Construction of i douse ru n
5-14 dll
Build lig Norse Insolation
5,20 dB
• Noise B iuriers - In certain cases,. It may be possible to acquire Ilsnited property rights Iar the constrwction of noise barriers at the receiver, As discussed above, barriers need to break the line -of -sight between the noise source and the receiver to be effective and are most effective when they are FEDERAL TMN IT DN NtSTPATM3N IGf
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closest to either the source or the receiver. See 5ectiory 3.3 for more Information on noise barriers_
• Building Insulation — In cases there noise barriers are not feasible --such as muhi-Story buildings, buik ngs very close to the ROW, or grade crossings the only practical noise mitigation measure may he to provide sound insudation for the buildings_ In these cases, the need for mitigation at locations where impact has been identified will depend on the use (outdoor vs, indoor), any eaxisting outdoor to indoor reduction in noise levels. and the Feasibility of constructing effective noise barriers for second stories and above
Depending on the quality of the original building facade, especially windows and doors, sound insulation treatments can improve the noise reductions from transit noise by 5 to 20 dB, To be considered cast-elfenlve, a treatment should provide a laburnum reduction a 5 dB In the Interior ref the building and meet the La, 45 dBA interior crlt ''Ion. Far nos r information, see Sections AI,
In marry eases, especially in locations with high ambient noise levels, the existing sound insulation of a building may already meet the 45 dBA La, Interior noise criterion, It is recommended that sound insulation testing, be conducted to determine if the existing sound insulation is sufficient or what additional measures waild be requited to meet the interior criterion, Effective treatments include:
• Caulking and sealing gaps in the building facade; and ▪ Installation of view doors and windows that are specially designed to meet acoustical trarsmiskion-ioes requirements:
- Exterior doors facing the noise source should be replaced with wel-gasketed, sold -core wood doors and well -,gated storm doors,
Ar, tical windows are typically made d multiple layers of glass with air spaces between to provide none reduction, Acoustical performance ratings are published in terms of Sound Transmission Class (STC) for these windows. It is recommended to use a minimum STC rating of 39 on any window exposed to the noise source,
These treatments are beneficial for heat insulation as well as for sound insulation, but acoustical windows are typically non -operable and central ventlbt'ron or air conditioning is needed, ii,m dents' preferences should be cc- idered_
If needed. additional building sound insulation can be provided by sealing vents and ventilation openings and relocating them to a side of the binding away from the rioiee source_ In eases where the noise sources IS low - frequency noise iron diesel lincomotivrA, it may be necessary to rrrtreaSe the MASS of the building facade fat wood -frame housr by adding a layer of sheathing to the exterior walls,
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Exannpfes d reskdenteal sound insulation or rail or hi hwa ' projects are Itm iec!_ However, much practical pvpFnence with sound Iresu'adore o[ buildings has been gained through grants for noise m rigttiorr to kcal airport authorities by FAA.
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SECTION Transit Vibration
5 This section presents the basic concepts of transit ground -borne vibration, also referred throughout this marital as simple "vibration," and low -frequency groundborneinc se that sometimes results from vibration. The steps for the screening and assessing of potential vibration impacts, of transit projects for FTA NEPA approval are described in the following sections.
The Source -path -Receiver framework for ground -borne vibration for a rail system illustrated in Figure r l is central to all environmental vibration studies, The train whee@s rolling on the rails create vibration energy that is transmitted through the track seaport systern into the transit structure. The vibration of the transit structure exeiti Lhe adJanEntground, creating vibration waves that propagate through the ground and into nearby buildings creating ground -borne vibration effects that potentially interfere with activities. The vibrating building components may radiate stwnd, which this manual refers to as ground -bonne noise_ Airborne noise from transit sources is covered lit Sections 134.5 of this manual, Gr€rrnd-borne noise refers to the noise generated by ground -borne vibration,
'AA") S1ru uraar Vbeab s
Radiated Sound
.`3 711 vibration
Propagation Pall,
Figure 5-I Propagation of Ground.8orne Vibration into Bulldingr This section contains the following:
■ Section 51 The ground -bowie vibration and none metrics used in this manual
■ Section 5:1 An overview of transit vibration sources
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TFLMS T NOISE AND Vf&RAT1ON IA'1PACT ASSESSMENT 31ANUAL • Section 5.3 An overview of transit vibration paths
• Section 5.4 An overview of receiver factors of tansit vibration and a discussion of the technical background tar ground -borne noise criteria
5. I Ground -Borne Vibration and Noise Metrics
Vibration is an oscillatory motion that can be described in terms of the displa€ement, velocity, or acceleration. Because the motion is oscillatory, then e is no net movement of the vibration element and the average of any of the motion metrics is zero. Displacement is the most intuitive metric. For a vibrating floor, the displacement is simply the distance that a point an the floor moves away Irom its static position. The velocity represents the instantaneous speed of the floor movement and acceleration Is the rate of change al the speed.
Although displacement Is easier to understand than velocity or acceleration. It Is rarely used for describing ground -borne vibration. Most transducers used for measuring ground•bome vibration use either velocity or acceleration.
Furthermore, the response of hurmans, buildings. and equipment to vibration is more acc{rately described Lining velocity or acceleration.
This manual uses the metrics outlined in Table 5. I for transit ground-bcrne vibration and noise measurements. computations, and assessment. These metrics are consistent with common usage ial the United States.
Table S-] Ground -borne Vibration and Noise Metrics
Metric
Abbrcxiation
Definition
Vibration Decibels
VdB
The vibration velocity [eve in decibel Icalo.
Peak Partlti v rxity,
PPV
The peak signal value of an cncillaung vibration velocity waveform Usually..,pritgiiked in Incheafsesrand In the United States.
Root Mean Square
rms
Th sq are root of the anti -armor avrsago of the squared amptitudo of the signal.
A -weighted Sound Level
dBA
A -weighted sound lends represent the overall noise at a receiver that is adjusted in frequency to approximate typical human hearing sensiOrity. This unit is used to characterize ground -borne noise_ The metrics in the table above are illustrated in figure 5-2. The components in the figure include:
• Raw signal - This curve shows the Instantaneous vibration velocity. which Ructirates positively and negatively about the zero point • Peak particle velocity (PPV) - PPV is the r X<WIlltrn instantaneous positive or negative peak of the vibration signal. PPV is often sued in monitoring of constr°uctlon vibration (such as blasting) since it 1s related to the sti cases that are experiencexi by buildings and is not used to evaluate human response_
• Root mean square (noes) velocity — Because the net average of a vibration signal is zero, the rms amplitude Is used to describe smoothed vibration amplitude. The rms of a signal is the square root of the FEDERAL TRANSIT ADMiNeT 1.ATr13N 114
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Figure 5.2 Vibrance Signal In Absolute Units
The PPV and rtes velocity are described in inches per second in the United States and meta a par second internationally with seal different reference values). Although it is not universally accepted, vibration is commonly e,pressed in decibel notation The decibel scale compresses the range of numbers required to describe vibration.
The graph in Figure 5-3 shows the rmns curve from Figure 5-1 expressed in decibels.
Vibration velocity level in decibels is defined as:
= 20log I—wJ
vref
where
Le = velocity level, Vdl3
= 'nu velndty amplitude
I at IO'faarsec in the USA
rr�r = I x I 0'tYru'sec irtcesnae cowl y`
Eq. 5- I
.Bemuse of the +earUnions In the reference quwititleit, It i. Important to he dear ahem what rafurwneequantity is hang ewd when spackf ing rniority 'aewlz. Ali A. -aka, 'winks in sign manual are referenced to I:xl4" Inchee'second
The ratio ai PPV to maximum roe amplitude Is defaced as the citest factor for die signal The crest factor a typically grater than 1.41. aithuugh a coat fstar of @ or more is not unusual far Impulsive shook scar grout-d•leorne vibtatton from traits, the crest lacavr is usually Ito S.
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j
•
tl t Z 9 1 6 e 7
Tlma
Figure 5.3 Vibration Signal in RMS Velocity Decibels
Ground -bootie noise occurs when v oration radiate through a building interior and creates a low -frequency sound, often described as a rumble. as a train passes by. The annoyance potential of ground -berme noise is typically characterized with the A -weighted sound level. Although the A -weighted sound level is typically used to characterize commrmity noises characterizing low - frequency noise using A-welghtIng can be challenging because the neon -linearity of human hearing causes sounds dominated by law -frequency components to seem louder than broadband sounds (sounds consisting of many frequency components. with no doretnant frequencies) that have the same A weighted ICI. The resuh is that ground -borne noise with a level of 40 dBA sounds louder than 40 dBA broadband noise. Because ground -borne noise sounds louder than broadband noise at the same noise level. the limits for ground - borne noise are lower (ate , stricter) than would be the case for broadband noise -
5.2 Sources of Transit Ground -borne Vibration
and Noise
Ground -borne vibration can be a concern for nearby neighbors el a trait system route or maintenance facility_ However, in contrast to airborne noise. ground -borne Vibration Is not a common environmental problem. It is unusual far vibration from sources such as buses and trucks to be perceptible, even in locations close to major roads- This section ciiuiissM Cnmrrie i sources of ground -borne vibration and noise.
Most perceptible indoor vibration is caused by sources within buildings such as operation of mechanical equipment movement of people, or slamming of doors.
Typical outdoor sowces of vibration waves that propagate through the ground and create perceptible grouted -borne vibration in nearby buildings include canstrtrction equipment, steel -wheeled trains, and traffic on rough roads. If the rosdway is fairly smooth, the vibration from rubber -tired traffic is rarely perceptIble, Building damage due to vibration is also rare let typical transportatton projects; hat In extreme cats, s.trh as during blasting Cr pile - driving during construction vl ration could cause damage to build ngs, Figure r4 illr trates curnmoon,eibration sources and tfte human and structt.-al response to ground -borne vibration ranging from approximately SO VdP i<bAr vit $5O51,N. TRAMIT ADP1tNt5TRATION i 13
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perceptibility) to I Co VdB (tile tfrnashold of potential damage). The background vibration velocity leve[ in residential areas is usually 50 VdB dot' loweroitiii and the:
threshold of perception for humans is approximately b5 Vd.3. A vibration level of 85 VdB in a residence can result in strong annoyance.
NunamIStructural Responas
loc t t4t71cal Sources
Lsesp (50 fl from source)
TI9rEshotd rrrr rrsh at 11 -Mgr r, r5alner, r, --
damage far tragic. buildings
DrPlFuky well tasks such as
rending a computer Screen
Ree*rrltie anntuart:r, IrafMuaf* —"
events it j. commute two
Retu I shall errluyran_e, Irrquert —�
r vents Js 4 rabid vamp
p
LIME far YYMCEI,, sensitise
eq.pmant.Amprde ttrashuldfar
rwmar, Darrepban rd Ntffsun
90 H4
ro
so
Bias -ling tram cansvuctan prciarts
Bulltlaxers and ocherbeay tracked
-_onsbuctan equipment
- commuter rag, upper ri ]
kalr a umrse upper amnge
- c4rrmuiier cal, t4Pkil
�— Bus minx* over hump
- Pawl banst typnearl
— art or duCkkgsce1
- Typical bac,t n]ur4 vtirahm
'rams W.Svmdon lAtr effy Lintel' in MEI redetrus to ra-e inchasadamid Figure S-4 Typkal Levu of Ground -Borne Vibration
Rapid transit or light rail systems typically generate vibration levels of 70 VdB or more rear their tracks, white buses and trucks rarely create vibration that exceeds 70 Vd8 unless there are bumps due to frequent potholes in the road.
Heavy Locomotives on ,diesel commuter nil systems mete vihttirn levels approximately 5 to I4 dB higher than rail transit vehicles.
Vibration from trains is strongly dependent on factors such as how smooth the wheels and rails are, as well as the resonance frequencies of the vehicle suspension system and the track support systetn. These systems, like. all mech'tiieal systems, have rrsonaricr that result in increased vibration response at ter tarn frequencies, called natural frequencies. Unusually rough road or track. steel -wheel flats, geologic conditions that promote efficient propagation of vibration, or velriclf5 with very stiff suspension systeiro could increase typical Background vibration b gplcaily well below the tfuesitoid of human perception ainda of coiuern only when die otrauon �tects miry semskire minab oateing car research stquiprrimmi deacon mkrusurpes and high-resukiion lithography egriprrsent are ercamples of equipment that is highly sensitive to vibration.
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vibration IeveIs by approximately ID Vrill Common factors that contribute to ground -borne vibration and noise at the source are presented in Table 5-2_ These factors are discussed in more detail throughout this Section.
Table 5-2 Factors that Influence Levels of Ground -Borne Vibration and Noise at the Source Category Factors
lnlfuence
Operations
and
Vehicle:*
Speed
Higher speeds result In higher vibrators levels- Doubling speed results In a sibradon level increase of approximately 4 to b dB.
Vehicle
sr pertdon
Stiff suspension in the vertical direction can increase the effective vibration larees. On transit cars the primary tuxpemtion has die largest effe4t on vebndau levels.
Wheel Wheel
Candtion
and Type
Eats and general wheel roughness are major sources of vibration from steel wheel/steel rail systems. I€eailient wheels on rail transit systems can provide some vibration reduction over solid steel wheels, but are usually too stiff to provide substantial reduction. For mote information, sec Section 4-4, Strap 2.
Guideway
TraretRoadway
Surface
Rough track or rough roads are often sources of excessive vibration. Maintaining a smmootfi surface will reduce vibration levels
Track Support
System
On 'ail systems, the track support system is one el the maker cQar 4ntalf# In determining the levels of vibration. The Highest vibration keels are created by track that is rigidly attached to a concrete traekbed fe.g, track on wood half -t es am bedded in the concrete). The vibration levels are much lower when special vibration control track systems suchas resilient fasteners, ballast irate, and II ii i ng slabs are need.
Transit
Striseture
)Heavier transit structures typically result in the lower vibration levels.. The 'eb'arlon levels from a iglvt vbw Jvt bored cannel will usually be hIgher than from a poured concrete box subway.
Transit System
Elevation
A rail system guideway will he either underground (silbway),, at-zrade or elevated, with substantial dIRarences in the vibseuorr characteristics at each elevation:
■ Underground: vibration Is typioilly the most important environmenlai factor of interest_
■ Augrader. airborne muse k typically the dominant facto-, although vibration and noise can be a problem particularly at anterior Iocations well isehtted from exterior noise
■ Elevate[[ it is rare for vibration co be an issue with elevated railways Except when guideway supports are located within SO ft of buildings.
Brief discussions of ground-bome vibration and noise stawrces for different nudes of transit are provided below_
As -Grade Heavy Rail and Light Pj
Ground-bprrve vibration and noise from urban heavy rail and LIT is cannon when there is less than 5{1 ft between the track and building foundations_ Loral geology and structural details of the building determine if the source of complaints is due to perceptible vibration or atdble ground -borne noise.
Complaints about ground -borne vibration from surface track aimore common than ground -borne noise complaints. A substantial percentage of complaints about both ground -home vibration and noise correlate with proximity of spacial track work„ rough or cornigated track, or wheel fiats. Light rail systems tend to generate fewer complaints than heavy rail dire to lower operating speeds. :FEDERAL TRAMIT AJDMiNtSTRAT*@N 114
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Commuter surd Intercity Passenger Trains
There k the potential for vibration -related r55ries when new cammaater or intercity rail passenger service (including electric multiple units (EMUS) and diesel multiple units (CMOs)) powered by either died or electric locomotives is introduced in an urban o suburban area. Commuter and intercity passenger trains have similar characteristics, but commutes hales typically operate on a more Ireeteent schedoile. ` hmee paeeengge tiaras often share track; with freight trains. which have different vibration characteristics as discussed below.
Freight Trains
Local and long-distance freight trains are similar In that they both are dliesel- powered and have die sance types al cars. They differ In their overall length, number and size of locomotives, and number of heavily loaded cars, However, became locomotive suspensions are similar, the maximum vibration levels of local and king-dstartee freights are similar_ Locomotives and rail cars with wheel flats are the sources of the highest vl briber levels.
If the transit project do not in any way change the freight service tracks, etc,. then vibration free the freight fine would be past r#f the existing cenditione and need to be considered In terms of cumulative Impacts (see Section 5.2. Step 3 on haw to consider cumulative impacts). If the project results in cheers to the freight path. operatione frequency. etc, (e.g., relocating freight tracks within the ROW to make room for the transit tracks) then those potential impacts and mitigation should be evaluated as part of thn proposed project. However. note that vibration mitigation is very di -Moult to implement Ctrl tracks where freight trains with heavy axle loads operate,
High -Speed Passenger Trains
Passenge, trails tievellieg at high speeds, 90 to 250 ivies per hour, have the potential for creating high levels of ground -borne vibration. Ground -borne vibration sherd be anticipated as one of the maser eiwiranrnentel impacts of airy trains li avelling at high speeds located in en urban yr efeburban area. Fee projects that are specifically high-speed transportation refer to the FRA "High - Speed Ground Transportation Noise and Vibration Impact Assessment' guidance mantual.sa'
AGT Systems
AGT systems include a wide range al transportation Cation vehicles that provide local circulation in downtown areas airports. and theme parks. Because ACT systems normally operate at low speeds, have lightweight vehicles, run on elevated structeres, and rarely operate in vibration -sensitiv=e areas, grczund- borne vibration problems are very rare_
Subway And At- ed Track
W3i a rot. d-honee vibration produced from trains oeetrating subway and at - grade track have very dlffere it clrar-aeterrsties, they have comparable overall vibration vette ty levels_ Complaints about grntnd-barns vibration are often rritOra common neer subways Pres moor at -grad track_ This Is rent because = Amtrak erilrn (IYranded A>:ela as the time d puLriciabn} art the North ( Coraidoor L trreeFl Bolton anti lAiatiro,gton, C. whkh *MP moderate to high Fpcad, in acme sections with IFly nr J [rack fit Ants thtF category. nDhRAL Tf idtt6IT ,e.DMANt5TRATrtaN I I5
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TRANSIT NOIRE AND VIBRATION It'1PACT ASSESSMENT 31ANUAL subways create higher vibration levels than at -grade systems, rather because subways are usually located rn more densely developed areas in closer proximity to bulling foundations. and the airborne noise is tonally a more serious problem for at -grade systems than the ground -borne vibration. Another 'difference between subway and at -grade track is that the ground -borne vibration from subways tends to be higher frequency than the vitiation from At - grade track, which makes the ground -borne noise more noticeable.
Streetcars
Complaints about ground -borne vibration from street cars are uneom man given that streetcars typically operate.at very low speeds (less than 25 mph)_ Because the rubber tires and suspension systems of buses provide vibration Isolation. It k traisuail for buses to cause ground -borne vibration at noise problems. For most issues with bus -related vibration, such as rattling of windows, the cause is almost always airborne noise and dite€tly related to ninning surface conditions such as potholes, bumps. expansion Pirrts, or other clisocintinuities in the rood surface (usually resolved by smoothirrg the discontinuities).
Buses operating inside buildings will likely cause vibration concerns for other building inhabitants. An example of this situation i5 a bus wander station in the same bulking as commercial office spate. Sudden loading of a building sJab by a heavy moving vehicle or by vehicles running over lame divider bumps can eateie intrusive building vibration.
5.3 Paths of Transit Ground -Borne Vibration and
Noise
Vibration travels from the source through the transit structure and excites the adjacent ground. creating vibration weaves that propagate through sail layers and rock strata to the foundations of nearby buldings. The vibration then propagates from the foundation throughout the remainder of the building structure. The vibration of the building structure and room surfaces can radiate a low -frequency rumble called ground -borne noise (Figure S. I Soil and subsurface co ritiltbm are known to have a strong influence on the levels of ground -borne vibration. Among the most important factors are the stiff'res,3 and internal dampirrg of the soil and the depth to bedrock. Vibration propagation is more efficient in stiff day soils. Shallow rock many concentrate the vibration energy dose to the surface, resulting in grtx'nd-bcfrrie Vibration problems at large distances from the tract€_ Factors such as soil layers and depth to water table can have substantial effects on the propagation of ground -borne vibration. Thee factors are summarized in Table r3-
quiEftAJ: PRAN'3IT At7MtlN'15TRATION I I$
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Table S. Facto- that Influence Leven orGround-bowie Vibration and Noise along Faith Geeoktgry Factors
Eeflutsnce
Soil type
VIbra on levels .ue }generally Nenei la.%Leff day -type soli than la loose sandy soil_ Vibration levels are usually high near at -grade track when the depth to bedrock is 50 ft or I. Subways founded en rock will result In lower vibration amplitudes dose to the subway. Vii+treon levels do not attenuate dt rapidly In rock ax in Anil.
Rotk layers
Soil' layering
Soil layering can have a sarbsranGsl effecr on Lee vibration levels since 'Pathstratum can have considerably different dynamic rharacrensilcs
th to water table
Dep definite
The Bence of the water table may have a substantial effect on vibration, but a relationship has not been established,
5.4 Receiver Factors that Influence Ground -
Borne Vibration and Noise
Ground-borrre vibration is a ecsncern almost inside buildings- Train Ahratksn irey be perceptible to people who are outdnor's but it R very rare for outcdoor vibration to cause complaints.
The vibration levels inside a building are dependent on the vibration energy that reaches the building foundation. coupling of the building foundation to the soil. and promotion of the vibration through die building. In gerieral, the heavier a building is, he lower the response will be to the Indolent vibration energy.
Common factors that contribute to ground -borne vibration and noise at the receiver are presented In Table S -4 -
Table 5-4 Factors that Influence Levels of Ground -Borne Vibration and Noise at the Receiver Receiver Building
Factors
Infiue roee
Foundation type
The heavier the building inundation, the greater the rpnrpl-ng loss at rho vibration propagates from the wound into the building
Building
construction
Each bulking Iran different characteristics relative to structure -bionic vibration., but In general. the heavier the building. the lower the levels of vibration. The maximum vibration amplitudes of the floors and walls of a budding will often occur at the resonance frequencies al the components al the building.
Acoustical
absorplirtn
The more acoustically absorptive materials in the receiver roam, the lower the graued•borne no level. Nate that becstne graund•bnrhat noise us*Fslly is a law• lc equeracfr pherwrnenon. it is affected by low.freriuency absorption fe g., bellow 250 Hz).
5.5 Hultman Response to Transit Ground -borne
Vibration and Noise
This section contains an overview of human receiver response to ground -borne vibration and Boise. It sues as background information kw the vibration impact cnteria in Section 6.2.
The effects of ground -borne vibration can include perceptible movement of floors in buildings, rattling of windows, shaking of 'items on shelves or hanging on walls, and Iow•frequency noise (ground -borne noise). Building damage is not a FEDERAL TRAMiT ADNiiNt5TRATIfyN I I7
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factor for typical transportation projects, but in extreme cases, such as during blasting or psle-riving die construction, vibration could cause damage to buildings. Although the perceptibility threshold is approximately 65 VdB human response to viibration is not usually substantial unless the vibration exceeds 70 VdB (Figure 5-4). A vibration level that causes annoyance is well below the damage risk threshold for typical btiiklings (100 Vtf$).
Ground -borne vibration is almost never a problem outdoors. Although the motion of the ground may be perceived, without the effects associated with the shaking of a building, the motion does not pnovoke the same adverse human reaction_ Ground -borne noise that accornpantes the building vibration is usually perceptible only inside buildings and typically is only an issue at locations with subway or tunnel operations where there is no airborne noise path or for buildings with substantial sound insulation such as a recording studio.
One of the ehallenges In developing suitable criteria for ground -borne vibration is that there has been relatively little research into human response to vibration and, specifically, human annoyance with bullring vibration. The American National 5'tarrekards institute (ANSI) developed criteria for evaluation of human exposure to vibration In buildings in I9B3,04 and the Intarrtatlnnal C]rgartirratIon far Standardization (ISO) adopted similar criteria In I9€9 and revised them iri 2003..02i The 2003 version of [SO 163l-2 acknowledges that "human response to vibration in Ibukidii 4i^ is very complex," It further indicates that the degree of annoyance cannot always be explained by the magnitude of Me vibration alone.
In some cases, complaints are associated with measured vibration that is lower than the perception threshold. Other phenomena a such as ground -borne noise rattling, +ritual effects such as moment of hanging objects, and time of day (e,g,, late at nighty all play some rate In the response of individuals, To urckrxtand and evaluate human response which is often measured by complaints, all of these related ellects need to be considered.
Figure 5-5 illustrates the relationship between the vibration vekxity level measured in 2.2 homes and the general response of the occupants to the vibration from measurements performed for several transit systettrs along with subjective ratings by researchers and residents. These data are published in the "State -of -the -Art Review of Ground -borne Noise and Vibration."t" } The figure also includes a curve representing the percent of people annoyed by vibration from high-speed trains from a Japanese study for comparison!' I Both the occupants and the people who performed the measurements agreed that floor vibration iri the Distinctly Perceptible range is unacceptable for a residence. The data indicates that residential vibration exceeding 73 Vd2 is unacceptable fora repetitive vibration source such as rapid transit trains that pass every 5 to 15 rnirrutes. The results from the Japanese study confirm the conduston that at a vibration velocity level of 75 to BO VdB, many people will find the vibration annoying, A Transportation Research Board (TRB) study of human response to vibration from 2009 also supports this finding and indicates that Incidence of complaints fall rapidly with a level decreasing below 12 VdE I}3ii4 )
FEDERAL TRANSIT ADriiiiNeorKATION I I8
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TRANSIT NOISE AAJD VIBRATION IMPACT ASSESSMENT MANUAL
Response to nealstentlei Building Vibration
4 to 1$ Rapid Tranail Trains por NOW'
IO
OtersyreeutY ..
yam,,
Pd/rYW'Te F.ipiW
[anIWtTraaos
6660 of II4dr osam
961ppnWto tlett'
Speed tram
60 66 re re es
Vibration Velcsay Level •- dB re t micro m,reeo
Figure 54 Response to Transit -induced Resldendal Vibration 60 40 a�
so
Fable 5-5 preserrrs the human response to different levels of end -borne vibration and noise on which the criteria presented in Section 6.2 are based.
The vibration level'.(VdB) is presented with the corresponding frequency assuming that the vibration spectrum peaks at 30 Hz or 60 Hx: xl The ground - blame noise levels (dSA) are estimated for the specified vibration velocity with a peak vibration spectrum of 30 Hz (Law Ereq) and 60 Hz (Mid Freq)_ Note that the human response differs for vibration velocity level based on frequency. F04 - example, the noise caused by vibrating structural components may cause annoyance e,mn though the vibration cannot be lek Alternatively, a low - frequency vibration tan cause annoyance while the ground -borne noise level it generates does not.
-'The #.weighted level period -borne noise ¢iii be estimated by applying A -weighting to therlbr-atbn velocity spectrum and by subtracting are additional 5 dB for a room with &erage xoustkal shvoopdan Since the Ameighdng at 31.5 Pia Is -37.4 dB. if the Tliaration macrtrua peaks at 30 Fit. the A.weghted sound lend wR 6e approximaetitlr 10 dE lower than Lire velocity Iev, L If the vibration sues -wan tasehs at SO 1-s. the A-*relgkted sound level will be apprcnarnatehr 25 dB lower than the relacttr lta el FEDERAL TRANSIT ADMaNt5Tf1ATION I I v
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TRMSIT NOIRE AND V RATION IMPACT ASSE SMENT MANUAL
Table 5-5 1 -lumen Response to Different Levels of Ground -Borne Vibration anti Noble Noise Level
—Cow Mid
Fir Fred"
A,pprraiimate drrrsirialel Iserr pxJun 'kW 'Harry bunion. Low - 25 d14A 40dBA frequencysound usual inaudibbe. Mid -frequency sound excessive for quiet sleeping ,1:ens.
ApproAt ate dividing ilne between barely peirnpcble and dlstlitody 35 dBA 50 r1BA perceptible. Many people find transit vita -anon at dris level annoying. l ow-irequengr Heise mlerable for aleeplrrg areas. Mid -frequency noise: excessive in most quiet occupied areas.
Vibration tolerable only if there are an infrequent number of events 45 dBA 60 dB.A p f-er day Low grrency noise' exta34ivtr.ror sleeping, areas. Mid. frequency noise: excessive even for infrequent events par some arselvldn_
.leoproxunans .else lave nrfien eihraeicn $perrr!rm peak is near r `, '"numnxrihae name evel ulreii xbratIo[ Wet rrbin peak is Bear fiD Ffz Vibration
Velocity Lein
65 VdE
75 VdB
35 Vdfi
Human Response
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TRMSIT NOIRE AND l§BRATION It'1PACT ASSE SMENT f1ANUAL
SECTION Vibration Impact Analysis
6 The FTA vibration impact analysis process is a multi -step process used to evaluate a project for potential vibration impacts. If impact is determined measures necessary to mitigate adverse impacts are to be considered for incorporation into the pr jecL'3'
The FTA vibration Impact analysts steps are summanted as ferrous and are described in the following sections:
6. I Determine vibration analysis level.
6.2 IDeter mine vibration Impact criteria.
Option A: General Vibration Assessment Criteria.
Option B: Vibration Impact Criteria for a Detailed Vibration Analysis
6.3 Evaluate Impact Vibration Screening Procedure
Step I: Classify project vehicle&
Strip 2 Determine project type,
Step 3: Determine screwing distance,
Step 4 Identify vibration-sensItive land uses,
6.4 Evaluate Impact Gene -al Vibration Assesrrrent,
Step I: Select base curve for ground surface vibration level, Step 2 Apply adjustments.
Step 3: Inventory y vibrarion impact.
6.5 Evaluate Impact Detailed Vibration Analysis
Step I: Characterize Existing Vibration
Step I Estimate Vibration impact
Step 3: Assess Vibration Impacts
Step A: Determine Vibration Mitigation Measures
A similar process for the noise Impact analysis Is presented in Section 4, After the noise and vibration analyses have been completed, assess coast, uction noise and vibration according to Section 7 and document findings according to Section Il,
6. L Determine Vibration Analysis Level
There are three levels of analysis to assess the potential ground -borne vibration and noise impacts resulting from a public transportation project- The approprate level of analysis varies by project based on the type and scale of the project, the stage of project development, and its eJwlrorimerrtal setting. These three levels are: the Vibration Screening Procedure the General Vibration Assessment. and the Detailed Valuation Analysis. T rem levels of vibration analysis mirror the levels of tenlse analysis discussed in Settli n 4.Z The Vibration Screening Procedure, performed first, defines the study area ❑f any subsequent vibrati<ar impact assessment. Whet e there is potential for F DERAJ: TRAMIT ACitliNtsTRATN3N 121
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TRANSIT NOIRE AND l§BRATiON It'1PACT ASSE SMENT t1ANUAL 'impact, the Genes -al Vibration Assessment and (Detailed Vibratioh Analysis procedures are used to determine the extent and severity of impact In some cases a General Vitiation Assessment may be alt that is needed. However, if the proposed project is near noise -sensitive land uses and it appears at the outset that the impact would be substantial,it is print to conduct a Detailed Vibration Analysis_
The methods for analyzing transit vibration are consistent with those dt�cribed in recognized handbooks and international standards,( "r Conduct the vibration screening procedure and then determine die etpprnpr+itrte vibration analysis opttiavr
Vibration Sct'een ing Procedure — The Vibration Screening Procedure is a simplified method of identifying the potential for vibration impact from transit projects, The Vibration Screening Procedure is applicable to all types of transit frlects and does rat require any specific knowledge about the vibration characteristics of the systrsn or the geology of the area. This procedure uses simplified assumptions and considers the type of project and the presence or absence of vibration -sensitive land uses within a screening distance that has been developed to identify most potential vibration impacts. it no vibratiornsensitive land uses are present with the defined screening dance, then no further vibration assessment is necessary.
The Vibration Screening Procedure steps are provided fn Section 6.1 Step I.
General Vibration Assessment — The General Vibration (Assessment is wed to examine potential impacts to vibrateon-sensitivelard use areas identified in the screening step o re closely. It uses generalized information likely to be available at an early st.-rge in the project development process and during the development of most enr-rirnnmental documents_
Vibrationlevels at recovers are determined by ,-timatirig the overall vibration velocity level and A•weighted ground -borne noise levels as a function of distance from the track and applying adjustments to account for factors such es track support syst+ ns, vehicle speed. type of builthng, and track and wheel conditions_ A General Vibeatlnn Assessment is suificiexrt for the envltrxnrnuetal review of many projects, including projects that compare transit modal alternatives or relocate a crossover or turnout. The General Vibration Assessment may also be sufficient if it results In a commitment to mitlgatitxr that eIJmirrates the vibration impacts, such as a charm in transit anode or alignment However, If Impact is identified through the General Vibration Assessment procedures and riot mitigated, a Detailed Vibration Analysts of the selected alternative must be completed. Most vibration mitigation measures can only be specified after a (Detailed Vibration ,Analysis has been done.
The General Vibration Assessment procedure t5 provided in Section 6.3, Step 2.
Detailed Vibration Analysts — The Detailed Vibration Analysis procedure is a comprehensive assessment method that produces the most acctrate estimates FEl7ERAL TRANSIT ADNI NISTpAT1ON 172
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TKAP+kSIT NOISE AND \ RATiON IMPACT ASSESSMENT NtENT MANUAL or vibration impact fora praposed proect and is often accomplished during the engineering phase of a project when there are sufficient data identiryirtg potential adverse vibration impacts from the project. However, a Detailed Vibration Analysis may be warranted earlier in the environmental review process if there are potentially severe impacts due to the proximity of vibration - sensitive land uses_ This type of assessment reitirin professionals with experience In performing and interpreting vibration propagation tests_ A Detailed Vibrator Analysis may not be necessary for all segments of a project Generalized prediction curves fi the General Vibration Assessment prercedur— may be si&fll cleric for most of the alignment and the Derailed VIbrration Analysis procedure may only need to be applied to partkctiarly sensitive receivers (Section 6.3). Note that a Mailed Vibration Analysis is typically required when designing special track -support systems such as floating slabs or ballast eats_ TI°it a and other costly vibration mitigation measures tan only be specified after a Detailed Vibration Analysis has been don in the engineering phase of the protect.
The DetuledVibaation Analysis procedure is presented in Section 6,3, Step 3. 6,2 Determine Vibration Impact Criteria
the the FTA criteria. prmented In this section when conducting a General Vibration Assessment or a Derailed Vibration Assessment. Like noise. the sensitivity to vibration varies by land use type, and the criteria represent these sensitivities. These criteria are based on national and international standards''" err"En as well as experience on fnrrnan response to building Vibration. See Section 5.5 for additional background information on the development of FTA vibration criteria. The criteria for environmental impact from ground -borne vibration and noise are based on the maximum root - mean -square (rms) vifirataan velocity levels for repeated events of the carne source.
Determine the appropriate criteria based on the level of analyses (Section b.I ).
The impact criteria for the General Vibration Assisi-rient are presented in Option A and the impact criteria for the Detailed Vibration Analysis one presented in Option B.
Option A. General Vibration Assessment 'Criteria
Determine the land use according to Step I and the frequency of events according to Step 2. The impact criteria for the General Vibration An?lysls are Ipresented in Step 3.
Step I: Land Use Categories
Determine the ©ppropeate bad rise category for the receiver of vibration impar5 of the project or proiect segment Sensitize land (Ise categories for'oibration assessment a:re presented In Table 6- I In order of sensitivity. Consider indoor of the buildings when determining land categories for ground -borne vibration and noise, since impact is experienced indoors.
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TRAPIFiIT NOIRE AND l§BRATION IMPACT ASSE Sl'IENT MANUAL Table r6 -I Land Use Categories for General Vibration Assessment Impatct Criteria Lanai Use
Category
Lased Use
Type_
Description of Lined Use Category*
;al
Buildings
This category includes special -use facilities that are very sensitive to vibration and noise that are not included in the categories below and rewire special consideration Hnwmrer, if the budding will rarely be occupied when the source of the vibration fe_g_ the train] is operating, there is no need to evaluate far impact Examples of these facilities include concert halls TV and recording studios. and theaters. 1 High
Sensitivity
This category includes buildings where vibration levels. including those blow the threshold of human annoyance. would interfere with operations within tie bulldog.
Examples include buildings where vibration -sensitive research and manufacturing* is conducted, hospitals with vibration-seematiive sgialpmerrt, and ureversitles conducting physical research operations. The builitnes degree of sensitivity w vibration is dependent an the specific equipment that will be affected by the vobratiran.
Equipment moderately sensitive to vibration such as high resolution lithographic equipment, optical Mier nsc pis. and elexcrcn ntieroserapes wish %brawn_ isolatirait systems are Induded in this category.wf For equipment that Is more sensitive, a Detnled Vibration Analysis must be conducted.
Residential
This category includes all residential la nil use and bindings where people normally sleep, such as hotels and hospitals. 'transit -,generated ground -borne vibration and noise irons subways or surface running trains are considered to have a similaT effect o.r recxiversr`r"
Institutional
This category includes institutions and offices that haws xibratio n sensitive equipment and have the potential for activity interference such as schools, churches, doctors r,irices. Camrnerpal or Industrial location: including ofFlr-e buildings are not included in this category unless there is vibration-seositeve activity Dr equipment within the bulldog As wlth noise the use of the building determines the Vibration sensitivity.
Maswfacwrierg of compxitar chips is a h einimpte of a vabr etiomsonskive process. ** Standard optical microscopes can be impacted at vibration levels below the threshold Pitmen Annoyance a4+ Even in noisy urban areas, the bedrooms wdl often be In quiet bulidings wah effective noise Insulation. However. grarrnd- boraar wheaten and eke are experienced indoors, end building uetupaots lure pra.tholly nu ro ems to reduce Ihelr exposure. Therefore occripants noire urban areas are lent as likely to be exposed to grour•1-barn* vrhnatlan an) noise at those in owlet suburban areas.
• Ground -borne 'Vibration — Locations with equipment that is highly - sensitive to vibration should be included in category I or assensed using the Detailed Vibration Analysis procedures (Section 6.3, Step 3) and criteria (Section 6.2, Option B)i or. specific criteria of the equipment manufacturer, Most computer installations or telephone switching equipment is not considered sensitive to vibration. Although the owners of this type of equipment often are concerned with the potential for grouted -borne vibration interrupting smooth operation ol their equipment, it is rare far computer or oth - eleztronic equipment to be particularly sensitive too vibration. This type of equipment is typically designed to operate in common building environments where the equipment may experience occasional disturbances and continuous background vlbiatlon caused by other equipment.
• Ground -borne Noise — Grouted -borne noise is typically, only assessed at Iocatsotes, with subway or tunnel operations where there is no airborne noise path, or roe buildings with substantial sound insulation such as a recording studio. For typical buildings with at -grade or elevated transit operations, the interior airborne nose levels are often higher than the iFEUERA1 TRAMIT 7�7MtlNt5TRATN3M1l I c4
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TRAPISIT NOIRE AND VTBRATION It'1PACT ASSESSMENT I1ANUAL ground -borne noise levels. For 'interior rooms or other speoiarl cases, ground -borne noise way need to he assesed.
Step 2: Identify Went Frequency
Dc ttrrnkJc IFre approprknc frequency or events for tiro project or probed segment.
Community response to vibration correlates with the frequency of events and, intuitively, more frequent events of low vibration Ievek may evoke the same response as fewer high vibration level events. This effect k accounted for in the ground -borne vibration and noise impact criteria by chatacteriarrg protects by frequency of events, Event frequency definitions are presented in Table 6 -2 - Table 6.2 Event Frequency Definitions
Category
Deflnldon
Typical Project Type
Frequent Events
More than 7D events per day
Most rapid transit
decisional Events
10-70 events per day
Mostcommuter trunk lines
Infrequent Events F+evrar than 10 events per day
Mastcflrnmuter rail branch Tines
Step 3: Apply impact Criteria by Land Use and Event
Frequency
Select the appropriate impact criteria for ground -borne vibration and noise based on the previously identified land use categories and frequency of events. It is also important to consider the time of vibration sensitivity. If the bulldkng Is ✓ ear typicaIEy occupied when the vibration Saii (e.g. train) k operating, kt Is riot necessary to corsider Impact.
The criteria in this section are appropriate far rise sing human annorence or interference with vibration -sensitive equipment for common projects. While not typical, existing conditions, Insight train operations, acrd bruilding darmage may require consideration.
• Existing Conditions -The criteria in this section do not consider ex stir conditions_ In most caws, the existing environment does ixx include a substantial number of perceptible ground -borne vibration or nois-e events, llowever, erastitlg conditions must be evaluated in some oases, such as for projects located in an existing rail corridor. Farr criteria coraldedng existing corxfitiorbs, see Step 3b.
• Freight Train Operations - The criteria are primarily based • oil wperience with passenger train operation. Passenger train operations (rapid transit. commuter reek, and intercity passenger railroad) create vibration events that last approrrtrrrately 10 seconds or less while a typical line -haul freight train event lasts approximately two minutes. This manual Is oriented to transit projects. However, situations will occur when freight train operations mist be evaluated, such as when freight train tracks are relocated kw a transit project within a railroA, ROW. Guidelines on applying these criteria to freight train operations are presented in Step 3c.
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TRANSIT NOIRE AhJD VlBRATION IMPACT ASSESSMENT MANUAL
• Building Damage — It Is extremely rare for vibration from train operations to cause substaiatiall or even minor cosmetic building damage However, damage to fragile historic buildings located near the ROW may be of concern. Even in these cases, damage is unrikely kept when the track is located very close to the structure. Damage thresholds that apply to these structures are discussed in Section 7.2, Step 4 or, Construction Vibration.
Impacts.
3a. Choose the impact'criteria by land use category and event frequency. The criteria for ground -borne vibration and rie a land i e categories I-1 are prated in Table 6-1 The criteria are presented In teams of acceptable indoor ground -borne vibration and noise lr,els Impact will occur If these levels are exceeded. Crftena for ground -borne vibration are expressed in turns of rills velocity levels in Vdl3.. and criteria for ground -borne noise are expressed in terms of A -weighted sound pressure levers in dl3A.
Table 6-3 indoor Ground -Borne Vibration (GBV) and Ground -Berne Noise (GON) impact Criteria for General Vibration Assessment
Land Use category
GBV Impact Levels
(WE re I mIcro-inch ?sec)
GBN Impact Levees
(dBA re 20 mlora Pxsciil3)
Frequent
Events
Occasional
Events
Infrequent
Events
Frequent
Events
Ckcasibnal
Events
Infrequent
Erupts
Category I' Wangs where
vibrraazion would intarllnrre with
interior operations.
65 VdB`
65 Vdli-
65 VdB'
NIA'
NA—
hi+A"
Category 2: Residences and
'mailings where people
normally sleep.
72¥0,
7"u V&
84 WE
3a d fit
38 dM
43 dd}I
Category 3: institutional lased
use. with primarily daytime
Lae.
7.5 VdB
70 VdB
83 Vd8
40 dE4
43 d0A
40 d0A
* Tins criterion IMilt is based on keels drat are scsppialw kr mast modeaately sensalve equipment set It as aaptis.al miermsope. Far eviipirtail drat is more aensieira, a Detailed Vibration Ansirsrs Mani be pat r to Vibration -sensitive equipment is generally nor sensitive to ground -borne noise. however 'fie reanntxturvr's sperikatIons should be reviewed for acoustic and vibration sensltasy.
The criteria for ground -borne vibration and noise for special land uses are presented in Table 6-4. The criteria are presented in terms of acceptable indoor ground -borne vibration and noise levels. impart will occur If UFiese levels are exceeded. As for the other land uses, the criteria for ground -borne vibration are expr+es-ser9 in terns of rms velocity levels in V+4s, and crrterta for ground. - borne noise are expressed in terms of got.nd pressure levels in dBA.
Table 6-4 Indoor (around -Borne Vibration and Noise impact Criteria for Special Buildings Type of 8ullding or
Room
Ground -Borne Vibration Impact
Levels ('VdB re 1 trhkro-inthfsec)
Ground -Berne Noire impact
Levels (dEA roe 2# micreh<Paicals)
Frequent
Events
OOtasbnrtl or
Infrequent Events
Frogtrent
Events
°coo€lanai or
Infrequent Events
Concert halls
_
E5 Vdil
65 VdE
25 dBA
25 dEA
Tit attaduha
65 VdB
65 VdB
25 dBA
25 dBA
Recording studios
65 Vda
45 VdB
25 dBA
25 dEA
Auditoriums
72 Via
SO VdE
20 dBA
313 dBA
Theaters
72 Via
90 VdE
35 dBA
43 dEA
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TRMSIT NOIRE AND l§BRATION II'1PACT ASSE SMENT I1ANUAL
3b. Consider the presence of existing vlbratfon conditions..
Whenthe project v iII cause webration mare than S dB above the ewsting vibration the existing source can be ignored, and the standard vibration criteria in Step 3a are appropriate. When the project will cause vibration less than 5 dB above the existing vibration level, use the instructions presented in this section to determine the appropriate irnpact criteria for the project For information on characterizing &lasting vibration conditions, see Section 6.4 Step 3.
Use Table 6-5 and Figure 6-I to determine the appropriate Impact criteria.
Sources of extsmng vibration are typscatly longer in duration than the events Introduced into the environment due to the project The frequency of use 1n the rail corridor is also a factor in characterizing the courting conditions. Both factors are considered in the process of determining appropriate impact criteria in Table 6-5 and Figure 6r I _
Exarnples cif projects considering the existing vibration conditions in Table 6-5 acrd Figure 6-I include:
• An automated people mover system planned fear a corridor with an existing rapid transit service with 220 trains per day that did not have a significant increase in events from the existing 220 trains per day and that Is not 3 dB above the existing vibration Ieve1 would cause no additional impact
▪ Where a new commuter rail line .shares a heavily -used corridor with a rapid transit system, the project vibration exceeds the existing vibration level. there is not a significant increase in the nu fiber of events, and the p -n ect vibration exceeds the escosting vibration level by 3 d13 or more, the projected vibration levels must be evaluated using the standard impact criteria to determine impact
• If a new transit prnjext will use an eulstIrig railroad ROW and the location of existing railroad tracks are shifted, existing vibration can be substantaal. The track relocation and reconstruction can resultin bower vibration levels that would benefit the receivers and not introduce am/ adverse impact I-lowever, if the track relocation ratrses higher vibration levels at vibration -sensitive receivers, then the projected vibration is must be evaluated using the standard impact criteria to determine impact.
MDERA. TRA IT ADMiNt5TRATICsN i r
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TRANSIT NOISE AND VIBRATION IMPACT ASSE Sf'IENT MANUAL
Table r5 -S Impact Criteria Considering Existing Conditions Category
Numberof Operations
(Aitprawait— whhautai shat)
Criteria
H �avi♦y
Used
More than 12 trains per stay
Use the standard vibration criteria in Section 4,a. Step 3a for the fosowing scenarios:
• The existing vibration does not itxr.eatd the standard vibration criteria
• The existing vibration exceeds the standard vibration criteria and clout is a slgrliileant Increase in events.*
• The existing vibration exceeds die standard vibration criteria, and the project vlbratxni Is 3 dB or mot a above the aid sting vibration.
The project. has ads impact it die existing vilx1. on exceeds the standard vibration criteria the number of events doesnot increase signif candy. and the project vibration does not exceed the existing vibration by a dB or more
Moderately
Used
5 — I2 trainsper day
Use the srandasd vibration criteria I n Section 6.2 Step 3a for the ♦olowang acenarru s'
• The eat -sling vibration does not exceed the standard vibration criteria
• The exsstirig vibration exceeds ire standard vibration cnterfa, and the project vibration k not 5 d'B or more below the existing vita Bn
The project has no impact if the Edsting vibration exceeds the. sundae d vibration crlreria. and the project vibration le at least S dB below the existing vibration.
ftifrequenely
Used
€cover than 5 trains per day
The standard vibration criteria in Section 6.3, Step 3a apply.
Approxlrnateiy doubling the number of evnaass IS regained far a slgulkanrt Increase:
aDhEtaL TRAMIT ADNIIINt5TWAT*ON I1°
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TRANSIT NOISE AND 'IBRA- ON IMPACT ASSESSMENT MANUAL
Figure 6-I Existing VihraYion'' Criteria Flow Chart
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3c, Apply criteria to freight trains if part of the protect.
Use the 'triter la presented in Step 3a to assess die vlbradori from height tr atns in shared ROW scenarios because rio specific impact criteria exist for freight railroads. It is important to consider that freght operations occur over suta tantiatly greater distances than passenger train operations and have different weight and axle loads.
When assessing vibration from freight train operation, consider the locomotive and rail qtr vibration separately. Since locomotive vibration lasts for very short tine, k can be chsiracteriaed by the infrequent events category in Tab is- - Rail car' vibration from a typical line -haul freight tram usually fasts for several minutes and can be characterized by the frequent events category in Table 6.2. Mote i Vila -Aloe IF abbreviated as -vb." In ties duwrilart, FbDERAL TI AMIT fliDNIIIN15TRATM3N 120
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TRMSIT NOIRE AND l§BRATION It'1PACT ASSESSMENT r1ANUAL
that locomotives often create vibration levels that are 3 tc B dB higher than those treated by roll Cars.
Use good engineering judgment to confirm die approach is reasonable for each project, For example, some spur rail lines carry very little rail traffic (sometimes only one tram per week) or have short trait's, in which case it may not be necessary to evaluate for irmrp'act.. If there is uncertainty in how to detertnIne the appropriate criteria, contact the FTA Regional office.
Decisions to relocate freight tracks closer to vi bradorrsenntive sites should be trade with the understanding that increased vibration due to freight rail may not lee passible to mitigate. Freight rail vibtation may not always be successfully mitigated by the same methods as rail transit systems.
Option B: Vibration Impact Criteria for a Detailed Vibration Analysis
Deternt im2 the appropriate impact criteria for ground -borne vibration and ground -borne praise for a Detailed Vrbrdtiop Analysis.
Step I: Ground -Borne Vibration
Cheese the epprseprlvte criteria bused on Fgure 6-2 and Table b-6.
Ground -borne vibration criteria presented in this section are more detailed than In the General Vibration Assessment The criteria are based on international standards for the effects of oabratlon on people related to annoyance and interference with activities in buildings: as well as industry standards for vibration -sensitive equipment Yaat The criteria in this section are used to assess the potential far interference or annoyance from building response and to determine performance of vibration reduction methods. Note that for highly -sensitive equipment, specific vibration criteria provided by the manufacturer supersede the criteria in this section.
The criteria are presented by category h Figure b-2 and are defined by international and Industry stiandardsiru4i These criteria define limits for acceptable maximum r iris vibration velocity level with a one second averaging time at the floor of the receiving building in terrors of a one tfrrd octave band frequency spectrum. Band levels that exceed a particular criterion curve indicate impact;. and therefore. rultlgitlon options should be evaluated considering the specific frequency range in which the trifatmeitt is frost effective. Interpretations of the criteria are presented in Table 6-6.
laDERA1 t'I AN3IT istnitNNt5TRATICkN I
01-28
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TRAPISIT NOISE AND Vf&RAT1ON IMPACT ASSE SMENT 31ANUAL
sae
Io
au
an
0 15 12.3 1I SI 55 31 G 4a
onrtnrdWave emdCert. rcru t,rtr,
al I3
rr:a*imr4r. ICI
ae.iddxrmI ,iI
VC -6
VCC
d 153
Figure fa -2 Criteria far Detailed Vibration Analysis
oe
Table 6-d interpretation of Vibration Criteria far detailed Vibration Analysis.
Criterion
Curve
Max l v,"
Vd'B
©escripgon of Lisp
Workshop (ISM)
90 Vsle
at,on that is distinctly felt, Appropoate for workshops and similar great not as sensitive to vibration.
afire (MO)
gq
Vibration that cm be lek Approprilm for oil -ices and simihr areas not as sensitive to vibration.
Residential Day
(ISO)
Resedenrlel i t4ghL
Operating Rooms
(ISO
Vibration that is barely fat. Adequate tor computer equipment and low - 78 prxwei° optical microscopes (up 60 20X).
F!
Vibration ss not felt, but round -borne noise may be audible inside quiet rooms Suitable far medium -power optical microscopes (:l00X) and other equipment Of row sensitivity.
VGA
bg
Adequate liar medium. to Iiigh•power opticalmicroscopes (400X). mitrobalances, opptin it balances, and similar i c.ialjted emipmenit V B
Adequate lot Willi -power optical Microscope DOriX) and iincrectian and lithography equipment to 3 -micron Poe widths 54 Appropriate kw most lithography and Inspection eiluipntent LO I •otticron detail size.
D
Ssatahle in most instances by the most demanding equipment Including electron microscopes operating to the limits of their capabilities.
VC
42 The most demanding criterion lor extremely vibration -sensitive equIpm+dnt,
MOM ur+Ad at I f a-ortasa am -rover R 4wgtwirl,. row 9 to Fb175l1A1 TRAMIT ADNIANI5TRATION 13I
01-28
Cent
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RTC -719
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TRIV4SIT NOIRE AND l§BRATION It'1PACT ASSESSMENT I1ANUAL In addruon to the tees described in Table 6-6, the detailteef vibration criteria cen be applied to the t]. rise land use categories presented in Table 6-3. • For residential land use {category 1i, use the residential night criterion curve in Table 6-6.
• Far institutional use {category 3}, use tine residential dray criterion curve in Table 6-6.
• For category I. the specific use of the building should be inatCiVed to tfie appropriate criterion curve in Table 6-6.
• For special buildings, such as those found in Table 6-4, ether the criteria in Table 6-4 or specific criteria presented by the building operator should be used.
These criteria use a frequency spectrum because vibration -related problems generally occur due to resonances of the structural components of a building or vibration -sensitive equipment. Resonant response is frequencyd ndent. A Detailed Vibration .Analysis can provide an assessment that identifies potential problems resulting from resonances.
The detailed vibration criteria are based on generic cases when people are standing or equipment k mounted on the floor in a conventional manner.
Consequently. the criteria are less stringent at very law frequencies below B Hz_ Where special vibration isolation has been provided in the form of pneumatic isolators, the resonant frequency of the isolation syatenn is very low.
Consequently, in this special case, the cm .ea may be extended flat at lower frequencies.
Step 2: Ground -borne Noise
Ground -berme noise impacts are assessed based on criteria for honor err ayaree and activity interference. The Detailed Vibration Analysis procedure provides vibration spectr inside a building. To evaluate ground -bonne noise, convert these vibration spear to sound pressure level sperm in the occupied spaces using the method described in Section 6.5 and compare to the criteria as follows:
• For f@Sidendal buildings, use the crit€r•ia panted in Table 6-3. • For special buildings listed In Table 6-4, A -weighted noise may not be sufficient to assess activity interference for a Detailed Vibration Analysis, Each special building may have a unique specification for acceptable noise levels and criteria must be determined on a case -by -use basis - For example, a reenrdirt studio may ITave stringent rpgtirermants for allawahle noire ire each frequency
6.3 Evaluate Impact Vibration Screening
Procedure
Determine the paterttkrl for Impart using the Itt ration Scretrily Procedure by identifying any vi&rt n -sensitive !arid uses {T1bie !t- ij within the trpprrpriote screening distance.
n DERair. tRAN'sIT A.DMiNtSTRATION 132
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TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT t1ANUAL
Ka Further 1 NGra4� Afl 4e
lMYd1 �Regarei ! Rewind
01-28
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Figure 5-3 Flow Chart of Vibration Screening Process
Step I: Classify Protect Vehicles
Determine the proyect type and the out step hosed on the gar tines Wow.
Option I No Vehicles - Transit projects that do riot Involve vehicle do not have potential for vibration impact and do not require further analysis (Box A in Figure 6-3).
Many smalls FTA-funded projects, such as bus terminals, park -and -ride lots, and station reliabditation are in this category, and do not requIra Irs-ther analysis of ground -borne vibration impact However, If track systems see modified (e.g., Us dcs moved or avditches modified), proceed to Step Z, (FEDERAL TRAMIT Ati,Ntifli5Tlit,eTioiNi I
Ritz -Carlton Rancho Mirage MND 11942
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RTC -721
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TRMSIT NOIRE AND VTBRATION Ir1PACT ASSE SMENT I1ANUAL
Option B: Stee-wheekdlSteel-rail Vehicles -Transit projects with steel- wheelediste la -ail veiides have potentb d for vibration Impact (T3ox 6 in Figure 6-3); proceed to Step 2. These noel systems include urban rapid transit LRT, commuter rail. and steel -wheel intermediate capacity transit (ICI-) systems, Option Ct Rubber -tire Vehicles -'For projects that involve rubber-bre veIucles and da root meet the following conditions, vibration impact k ur�llkely, and no further analysis is needed. Proeeesf to Step 2 for protects that involve rubber -tare vehicles and meet the following conditions (i3ox A in Figure 6.3); ■ Roadway irregularity - Expansion loins, speed bumps, or other design 1eattt that result in uiwevenruNs in the road surface tar result in percetibie ground -borne vibration ar distances up to 75 ft away. • Operation close to v►ibralion-sensitive buildings - &csr , , trucks, or ati em Imeavy vehiclesape-sting dose to a vibration-sentltive building (within approximately IOC ft from the property Line) may impact vibration -sensitive artivtties, such as research that uses electron mim.. uscopes or manufacturing of. computer chips.
• Vehicles operating within buildings - Special considerations are often required for shared are facilaies where vehicles operate inside or directly underneath buildings such bus stations located inside an office lwilding complex.
Step 2: Determine Project Type
Determine the project type acoardiog to Toddle 67-
IFUDER,AL TRAMIT ADMiNt5TRATmON I 44
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RTC -722
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TIW4SIT NOIRE AND lt8RAT)ON IMPACT ASSESSMENT MANUAL
Table 6.7 Project Types for Vibration Screening Procedure Project Type
Number
Project
Type
f3eAcrlptfaas
I
orwe r[ibnal
Commuter
Railtaud
Bath locomotives and Irsssenger vehiclt create vibration.. For commuter trams. the highest vibration levels are typically created by the locomotives Electric rnmmiser fill vahldes areare levels of grouid,borne vlbratfoai that al t- comparable to itlek-Oic r;tpid transit 4ebrtles.
2 RPLT
Ground -borne vrbratron impact'rram rabid transit trains is one of the major eisirirt nutenta.l issues for new systems_ Ground -borne vibration Is usually a. .odor vonitern for subway operations. It is less common fill" at -grade and elevarad rapid tramit lines to create intrusive grovrnd-burrrl± vibration and I noise since air -borate noise typically dominates,
3 LB T #
Streetcars
The ground -borne vdhration characteristics. of 1 -.ghat rail systems are very similar Ell tiiaaa of rapid transit systems. Because the speeds of light rail systems are usually lower typical Wbration levels are usually lower. Steel-,vbeelJueef-rail ACT as rnduded in either Opt category or the ICT category depending on the level of service and train speeds.
4 Intermediate Because
Capacity
Transit
at the low operating speeds of most ICT
T systems, vibration problems
are not common. However. steel -wheel ICT systems that operate dose tos' vibration -sensitive bulb:rings have the potential of wising intrusive vtbi°ation,.
With a stiff suspension system. an ICT system could creates intrusive vibration.
Bus and
(lubber -Tire
Transit
Pio sets
This category encompasses most projects that do not indude stem -wheel trams of some type. Examples luclu & diesel bum. electrk trolley buses, and rubber -tired people movers, Most projects that do not include steel -wheel norm do not came Almadon impacrs'i"°
+ia® tliy striamll distarxtu I r c3c sA+a.y I land !awe n Table b as I^lttst complaints ablaut vibration caused by buses and truck are related to rattling of windows of Items hush giro she waAs.
There vabratitrrm ane usually the result of airborne noise and not graved -borne vetwatlon In the case where groiuid-boars vibratrem le the courts of the rcrrrphlet, the vlJrraeior; can usually be.. etrannitd to irreger1aritaa ie the toed Step 3z Determine Screening Distance
Determine the approP•aiotc screening distaners blued on land core owl project type elctterdmg to Tobir 5-8.
The distances are based on the criteria presented in Section b•3, the procedures in Section 6,4 assuming normal vibration prErpagation, and include a 5-4B factor of safety. Evian so, arms with very efficient vibration propagation can have substantially higher vibration levels_
Because of the 5 -decibel safety factor, the screening distances will identify mast or the pot,errtrally impacted areas, even for areas with efficient propagation However, when there is evidence of plfleirbrat propagation, such as previous iwrnplaints about edstIng transit facilities or a history ot prabterns with.:
constr.iction vibration, increase the distances in Table 6-f3 lair a factor of I.5- aDERA1 TRANSIT aDfliNI5TRATIC3N 13`.
01-2$
Cc fit
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2552
RTC -723
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TRAPIfiIT NOIRE AND VIBRATION It1PACT ASSESSMENT I1ANUAL Table 6.0 Screening Dli tames for Vibration Aires smother' Type of Pra9j0
Critical Distance for Land Use Categories'
Distance From
Land Use
Cat 1
ROW or Property
Land Use
Cat. 2
Luc., ft.
Land Use
Cat 3
Cormentinnil Commuter Railroad
600
200
I20
RRT.
600
200
[20
Lill- and Streetcars
450
LSO
[00
ICT
200
100
SO
Bus Projects lie not 3revioarsly screened out)
100 SG
—
For idea VIN nt'Sereenli g'Pnuxedere, evaluate special bulldlexsas dalrs»ue: Ca te l 1 - concert halLwad TV swdioe. Category 2 - rtteatecs and avditraritenn
Step 4: Identify Vibration -Sensitive Land Uses
Identify all vilaratiotrsereitive land asses (Table 6- I } within the chosen screening distance, If n0 vibration -sensitive land uses are identified, no Further vibration analysis rs needed_ If one or more of the vilxailon-sensItivra land usa≥s are In the screening distance. compete a General Vibration Assessment (Section 6.4) or a Detailed Vifxatton Analysis (Section 6,5).
6.4 Evaluate Impact General Vibration
Asses nlent
Erakrste for impact using the. Gerrerrsl Vibration Assessment proceaiure if the irrhrarrion Screening Procedure (Section 6.3) identified vibrotlarn-sensitive receivers witltm the screening distance 4 the transit vibiciikut source,
For gui i lines on when the General Vibration Assessment is appropriate:
review Section 6.I
The basic approach for the Genea'al Vibration Assersmerd is to Mile a curve or set of curves that predicts the overalI gratinii.borne vibration as a function of distance from thre source. then aipply adjustments to there curves to account for lectors uUch as vehicle speed, geologic conditions, building type, and receiver location within the 'building: When the vehicle type is not covered by the curves included in this section, it will be iiiecessary to define an appropriate curve either by extrapolating from existing linlonmation or performing measurements at an existing facility,
Step I; Select Base Curets for Ground Surface Vibration Lend
Select a standard vibration curve to re -preset -1i general vibration rharacteriitk for the source.
The curves presenter in Ftgure 6-4 are biased on measurements of ground- bor rhe vibration at representative North ?wrier ic t transit systems and can be used to represent vibratican characteristics for standard transportation systems in the General Vibration Assessment
nDERAL TI AMIT AL7MiNa5TRAT* N 174,
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TRANSIT NOISE AhJD V RATION IMPACT ASSESSMENT MANUAL
These curves assume typical ground -borne vibration levers, equipment In good condition, and speeds of 50 mph for the rail systems and 30 mph for buses_ Adjustments to account for differences iii speed and geologic conditions are included in Step ].
Select a baise curve from Figure 6-4 according to the guidelines in Table 6-9_ Equations for the a irvee in Ftg wro 6-4 are Itacluded in Table 6- IC. Additional considerations for selecting a base curve for systems not included in Table 6.9 are presented below by transit mode.
Table 6-4Ground Surface Vibration Level Base Curve Descriptions Curve
Cieseriptian
LocomotivePowered
Passenger or Freight CQrv6
Appropriate or vehicles powered by close or electric locumotiveaincluding intercity passenger trains and committer rail trains.
Raped Transit or fight Rail
Vehicles Curve
Apprc prate for both heavy and light rail vale Iles on at-giade and subway track
Rubber -Tired Vehicles Curve
Appropriate for rubber -tire vehicles_ These types of vehicles rarely create ground -borne nibration prob emi unless there is a dlncenumuty or bump In the road that causes the vibration This curve represents the Vibration level far a typical bus operating on smooth roadway..
lea
56 a 513
8 gri
75 a
7a
ro
C3
€0
dr
55 50
10 ;d0 30 40 50. ELI cif lee 150 200
Distance tram neon o nteerine, it
Huse dirxyinnl disrinre for ierssrermind CyJ_2en-ei-
Figure 6-4 Generalized Ground Surface Vibration Curves
see
FLDERAL TRa tsiT aciNuNisTRATION I37
01-28
Cont.
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RTC -725
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TI APISIT NOIRE AND l§BRATION It'1PACT ASSE SMENT 31ANUAL Table 4-1 Q Generalised Gr rund Surface Vibration Equations Curve
Equation
LatTlerIEStJVE Powered
Passenger or Freight Curve
I. =132,28+ 14,r1I In'gi;flij — 14.171nngtl.?)2
+1,6519.g1M3
Eq. 46- I
Rapid Transit or Light Raii
Vehicles Curve
L„ = ₹65,88 — 1,Iir.10(D) — 232 log ffl}I
—p_E#F dng,(D3
Eq. b-7
Rubber-.7lred 'Velt6descurie
«='56,48 +3428Inglih)-3t1.,251ngW )
+5.44) lgd(A)
Eq. 6-3
L., = vduelty level. Yin%
I) = art t,bnce. It
Considerations far selec-ring a base curve fear dlffesreet trWnsit modes include:
• Intercity passenger trains — Although Intercity passenger trains can be an Important source of environmental vibration, it is rare that they are~ considered for FTA-funded projects unless a new transit mode uses an existing rail Alvin -lent. When a new transit line uses an existing rail alignment, changes in the intercity passenger traffic can result in either positive or negative impacts, Use the locomotive -powered passenger or freight curve for intercity passenger trains unless there ate specific data. available on the ground -borne vibration created by the new train operations.
• Locomotive -powered commuter rail — Use the locomotive - powered passenger or freight curve for all commuter rail system powered by either etresel or electric locomotives.
+ Electric multiple unit (EPIU) — Use the rapid transit or light rail vehicles c-trvre for self -powered electric commuter rail tarns, e multiple unit (DMU) — SSr i.'f-pnwwed DM Us create Vibration Ie els snrnewhere between raped transit ve1ticiii and locomotive - powered passenger trains. A vibration curve for IDMUs ain be estimated by lowering the locomotive -powered passenger or freight curve by 5 dB..
■ Subway heavy rail or light raft — Use the rapid transit or light Hall vehicles curve for subway heavy rail and subway light rail, Although vibrations from subwray and at-gradetracks have very different characteristics, the overall vibration velocity levels are comparable.
When applied to subways, the rapid transit or light rail vehitles curve assumes a re:lativeiy lightweight bored concrete tunnel in sail. The vibration levels will be lower for heaver subway structures such as curt - and -cover box structures and stations.
▪ At -grade heavy* rail' or light rad, — Use the rapid transit or light call vehicles eats ee tor at -grade heavy rail or light rail. Heavy rail mid LR,T .44i -ides have similar suspension systems and axle loads and create similar levels of ground -borne vibration.
Fki7ERAL TRANSIT ADNI Nt5rftaTI0N 138
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TRMSIT NOISE AND VTBRATION IA'IPACT ASSESSMENT MANUAL
• Elevated guideways or atrial structures - Vibration Fran operations on an AL...ated st3 ucture is typecaiFy not an Issue unless the guideway is supported by a building or located very close to buildings.
Apply the appropriate adjustment for the aerial structures (Section 6.4, Step 2),
• Streetcars - Use the rapid transit or fight rail vehicles curve for street cars.
• ICT - Use the rapid transit or light rail vdrekes curve for ICT systems with steel wheels and the rubber -tired vehicles curve for ICT systems with rubber tiros:
• Other vehicle types - For Ins common modes such as magnetically - levitated vehicles (magilsev), monorail, or ACT, use good engineering 'judgment to cheese a standard curve to best fit the movie or if a new curve needs to be developed, as a function, of distance from the owl" Examples include:
Vibration fnaarrr a rubber --tire monorail operating on aerial guideway can be approximated using the rubber -tired vehicles carve with the appropr late adjustment for the aerial sti uctur+e (Section 6..4. Step 2).
c Mast of the data available vn the noise and vibration cJtraracterlstIcs d Smagte+v veticlel cesm from high-speed systems intended for inter -city MIMice. Even though there k no direct contact between the vehicle and the guideway, the dynamic loads on the guideway can generate ground -borne vibration. Measteements on a German Irg rspeed mag6ev
resulted En ground -hot ne vibrations at 75 rnph which is comparable to the base curve for rubber -tired vehicles at 30 mph, qtr
Step 2: Apply Adjustments
pi}` pro -speufirc adjustments to the swanked vibration curve.
Once the base curve has been selected, use the adjustrne3rrts in the following instructions to develop project -specific vibration projections at each receiver, All adjustments are given as single numbers to add to, or subtract from, the base level_
Adjustments are separated by source, path, and receiver and Include speed, wheel and rail type and condition, type of track support system. type of building foundation, and number of floors above the basement level. Calculate the appropriate adjustments to the base level. An example of the General Vibration Assessment Is provided at the end of this Section.
It should be recognized that many of these a;dustirecarts are strontgly decedent on the frequency spectrum of the vibration source and the frequency. dependence of the vibration propagation. The adjustments In this section ate suitable for generalized evaliration of the vibration Impact and vibration FEDERAL TRANSIT ADMaNa5TP.ATrpN 13e
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Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
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RTC -727
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TRANSIT NOISE AND Vf6RAT1ON IMPACT ASSESSMENT MANUAL
m Itigatkin measuri because they are based on typical vibration spectra.
However, these adjustments are not adequate for detailed evaluations of impact of vibration.sensitivet buildings or for detailed specification of mitigation measures,
2a. Apply source adjustments to the base curve using Table 6a -f I and the descriptions b .ktrw to account for the project -specific source characteristics.
Table &-f I Source Adjustment Factors for Generalized Predictions of GB Vibration and Noise Source
pastor
Adjustment to
Propagation Curve
Comment
%seed
Vehicle
Relcrrnc-r
50 inph
+1.6 dB
0.0 dB
f.9 dB
-i.4 dB
-a.9 dB
Speed
30 molt
Vibration level is approximately proportional to
2171 fs d� 6-4.
o81s f k see q
Ilrad
6f] "'I'
50 mph
40 mph
30 mph
2f] rriph
+6.4 dB
+-0.4 dB
+13 dB
Q dB
=3.S dB
Vehicle Parameters (not additive, apply greatest value only) Vehicle with
stiff primary
suspension
as dB
Transit vidrleie t with stiff primary sarspeaisions Nabe beech shown to create high vibration levels. Include this
adjustment when the Omar/ suspension has a vertical
resonance frequency greater than I5 Hz
Resiient
Wheels
dS
Resilient wheels do not generally affect ground -borne
vibration except at frequencies greater than about BO
Hz.
Worn Wheels
or Wheels with
Flats
+:14 dB
Wheel hats Or wfheds thg are unevenly worn can cause
high vibration levels.
Track Conditions (rot additive, apply greatest value only) Worn or
Corrugated
Transit
+1d dB
Corrugated track is a common problem. Mill stale* on
new rail can cause higher vibration levels until the rail has been in use for scene time if there are adjustments for vehicle paramiliters and the track Is warn tir
corrugated, only include one Abetment.
Special
Trar1 work
within 200 i[
+10 d8 (within 100 ft)
`5 dB (between IGA and 200 ft)
Wheel impacts at special tratiewark will greatly lueraeair. vibration levels. The increase will be less at greater
distances frwn the -tack. Du clot include an adjustment for serial tracicwurk more than 200 ft away.
Jointed Track
3, dB
jointed track can caber higher se -brawn levels than
welded track.
Uneven Road
Surfaces
I + dB
Rough roads or expansion inIrlts ate sources or
increased vibration for rubber -ire tnaneit_
Tuck Treatments (net additive, apply greatest value *sly] Boating Slab
Trau$bed
-15 ds
The reduction achieved with a floating slab vacated is
strongly dependent on the frequency charaeterisucs of
die vibration.
Bakst Mats
LLI ds
�
Actual reduction Is strongly dependent on frequency' DI vibration.
Hlgfi.Ri siOeiiee
Fasteners
-5 dB
Slats track with track fastened that are very cosmpliant In the vertical direction can reduce aibraiian at frequencies greater than 40 Ha.
•Mal stain on a raw rib is s slightly corrugaeed condition caused by certain steel mil taichnicium_ :FEDERAL TRAMIT aDriiNISTRATM3N Ile
01-28
Cont,
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RTC -728
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TFLMSIT NOIRE AND Vt&RATION IMPACT ASSESSMENT MANUAL
In addrtioh to the commons in Table 6- I I, use the fallowing guldelimm Lo select the apprnpriase adprstfrrent factors_ Some adjustments in the same ,itegory are not cumulative (additive) and only the greatest applicable adjustment should be applied. The adjustments that are not additive are noted in Table 6- I M and in the descriptions below. Note that some adjustments are not additive aicros€ multiple categories and are noted in the comments of Table 6 -I I. For example:
the adjustment for a vehicle with stiff primary suspension is 8 d and the adjtrstmeint for wheel flats is I fl dB, If the vehicle has a stiff primary suspension and has wheel flats, the ,projected vibration levels should be increased by IQ d8.. not 68 d9.
In addition, some Ablation control measures are targeted for specific lieciowcy ranges. The shape €3f the actual vibration spectra should be considered so that an appropriate vibration control measure may be selected, Speed - The levels of ground -borne vibration and noise vary, approximately, as 20 times the logarithm of speed. This means that. doubling train sperm will increase the vibration levels approximately 6 did, and halving train speed wil I reduce the levels by 6 d13. The adjustments in Table t- I 1 have been tabulated far reference vehicle. speeds of 30 mph for rubber -hied vehicles and 5O mph for steed -wheel vehicles. Use the following relationship to calculate the adjustments for other Speeds -
speed
rtdf�ac�� We) = 2DIrrgQ d r y
Variation with speed has been observed to be as low
as 15lst ( .apr"r )• but unless specific speed data for vibration for a vehicle has been obtained, use Eq. 6-4
Eq. 6-4
• Vehicle Parameters — The most Important factors for the v heir are the suspension system. wheel condition,and wheel type. Most new heavy mil and light rail vehicles have relatively soft primary suspensions.
However, a stiff primary suspension (vertical resonance frequency greater than 15 Hz) can result in higher levels of ground -borne vibration than crab primary suspensions. Vehicles, for which the primary suspension consists of rubber or neoprene around the axle bring, usually have a very stiff prmary suspension with a vertical resonance frequency greater than 40 Hz or more.
Deteriorated wheel condition k another factor that increases vibration levels, It can be assented that a new system has vehicles with wheels in good condition. When older vehicles are used on new track it is important to consider the condition & the wheels, and It may be appropriate to Include an ariustrnerit for the wheel corrditimn.
Re$ill€nt wheels will reduce vibration levels at frequencies greater than the effective resonance frequency of the wheel_ 'When this resonance al:ARAL TRAMIT ADNUNI5TRATrr3N 141
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November 2024
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RTC -729
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TRMSIT NOIRE AND l§BRATION It'1PACT ASSE SM'iENT I1ANUAL frequency rs relatdveiy high, greater than fad Ht, resilient wheels map only have a marginal effect ❑n ,ground -borne vibration.
The adjustments in this categ:ury are not additive: apply the greatest applicable value only,
• Track Conditions — This category include s the type a rail (welded, jointed, or special ttaclawork). the track support system, and the condition of the rail. The base curves assume welded rail in good condition. Jointed rail teases higher vibration levels than welded rail and the increase depends an the coirdltiee of the joints.
Wheel impacts at special trackwork. such as frogs at crossovers, create much higher vibration farces than typical track conditicrrr3s, Because of the higher vibration levels at special trackwork, crossovers are the principal areas e1 alteration impact on view systems. Methods of mitigating the vikrrat en impact include modifOrig the track support stem, installing low -impact frogs, or relocating the crossover_ Special track. support sirsterns such as ballast mats, high resilienice track fasteners, resiliently supported ties, and floating slabs have all been shown to be effective in reducing Oblation levels.
The condition of the running surface of the rails can strongly affect vlb orlon levels_ Factors such as corrugations. general wear, car mill scale on new track can came vibration levels S to 15 dB higher than normal.
MITI scale will typically wear away after some time In service, but the track must be end to remove cornigatians or to reduce the roughness from wear_
Roadway surfaces in the rubber -tired vehicle base curve are assumed to be smooth. Rough washboard surfaces, bumps, nr tmeven ieepareion jeiints are the types of running surface defects that cage increased vibration levels over the smooth road condition
The adjustments in this category are not additives apply the greatest applicable value Only, If there are adjustments for vehicle parameters acct the tracts k worn or corrugated, only include one adjustment_ 2b. Apply path adjustments to the base curve using Table 6.12 and the descriptions below to account for the project-speeific path characteristics.
F DERAL TRAMIT ADNIANt5TRATItesN I
01-28
Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2559
RTC -730
Responses to Comments
TRANSIT NOISE AND VfBRATION It'1PACT ASSESSMENT t1ANUAL Table 6-11 Path Adjustment Factors for Generalized Predictions of GB Vibration and Nuke Path Factor
Ad ustnnentto Frorajatiion Curve
Comment
Resiliently
Supported
lies
Vibration
Track, I -VT)
=10 dB
Resilient) ti stems have been
y supported y
dtund to Provide very effeetive control of
low -frequency vibration.
Track 3ttucttn•e (not additive, apply greatest value only} Type of
Transit
Structure
Relative to at -grade tie JB ballast
Flevaced structure
Open cut
- I B dB
0 dB
kr genera% the heavier the structure_ the
lower die vibration levels. Petting the track
In cut may reduce the vibration levels slightly.
Rack -based subways genrsafe higher -
frequency ihranon_
Relative to bored subway tunnel
Station
Cut and Coves
notk•has
Fn salt
-S dB
-3 dB
•1.5 dB
Ground -borne Propagation Eifecl3
Geologic
m rnrlitir?ns that
pram' t
eYlinerat
vibration
Propagation
Effiaent propagation In soII
+ IO dB
Bcitr to the text forguiCrutce on identifying
areas where efficient propaa&atiet] is possible
Propagation 100
1n rock least
alt.
SO it
ft
150 it
200 k
ettill
+2 dB
+4 dB
+6 dB
+9 dB
The Positive adjustmentucnuarts for ate
lower attenuation of vibration in rock
compared to Sail, It is generally more difficult
to excite vibrations in rock than in soil at the
source.
Coupling to
h,eldirrg
foundation
Vvood• rxme Houses
L.-2 Story Masonry
7.4 StayTasbRry
Largo Masonry on P'IGs
Large Masonry oat Spread
Footings
Foundation in Rode
. -5 dB
-7 dB
3 dB
I6 dB
_ 13 dB
0 dt.
kt general. the heavier the building
construction tiregreater the cooping lass
In addition to the comments in Table 6- I2. use the lollowir g guidelines to select the appropriate zdJustmerrt factors.
• Track Stnbcttttre — The weight and size of a transit 5trucvure affects the vibration radiated by that structure. In general, vibration levels are lower for heavier transit structures. Therefore, the vibration levels tram a cut -and -cover concrete double -box subway sin be assumed to be lower than the vibration from a lightweight ctancrede-fined barred darnel The vibration 4rom elevated structures is lower than from at•grade track because of the mass and damping of the structure and the extra diistarnce that the vi6ratllo.}- trust travel before it reaches the receiver.
Elevated structures m AGT applications are scrmetin1es di tgned to bear on building elements. This is a special case and may require detailed design consider3tio s.
The adjustments in the category are not additive; apply the greatest ap#lia hle value only.
FEDERni. T IT i.WreNisTRATsryN Ia7
01-28
Cont
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2560
RTC -731
Responses to Comments
TRAP T NOIRE AND l§BRATiON IA'1PACT ASSESSMENT r1ANUAL
• Ground -Borne Propagation Effects — Geologic Conditions — Although it k known that! geologic conditions have a considerable effect on the vibration levels, it is rarely possible to develop more than a general understanding of the vibration propagation characteristics for a General Vibration Assessment. One of the challenges with identifying the cause of efficient peopagatioe is the difficulty in determining whether higher than 'normal vibration levels are due to geologic conditions or due to special source conditions a gR nil corrugations or wheel flats), Some geologic conditions are repeatedly associated with efiicier7t propagation. Shallow bedrock, less than Q fir below the surface, is likely to have efficient propagation, Sall type and stiffness are also Important factors in determining propagation characteristics. In particular, stiff, clayey soils, consolidated sand, gravel, and glacial till can be associated with efficient vibration propagation. Investigation of soil boring records can be used to estimate depth to bedrock and the presence of problem soil corrclitiorrs.
A conservative approach wQurd be to use the ro-dB adittstment for eII1d iit propagation for areas where efficient propagation is likely_ However. this adjustment can greatly overstate the potential for vibration irnpact where efficient propagation is not present and should be applied usinggvod judgment- Review available geoleygiroil data and any compiahit history morn existing transit !Ines and major construction sites near the transit corridor to identify aromas where efficient propagation is possible. Il there Is reason to suspect laden( prropagatien conditions, conduct a Detailed Vibration Analysis during the engineering phase and include vibration propagation tests at the areas with potential for effloient propagation_
• Track Structure and Geologic Condttiotss - Examples
Subway
[Cr a subway, determine if the subway will be founded in bedrock.
Bedrock is considered to be hard rock. It is usually appropriate to consider soft siltstone and sandstone to be more like soil than hard rock_ Whether a subway is founded in sail or rock can make a 15 - dB difference In the vibration levels_
When a subway struewi a is founded in rock, include the following Track Structure and Ground -borne Propagation Effectsadltlbtnents from Table ie 12
- Type of Transit Structure adjustment: Rock -based - I5 dB - Geologic Conditions adjustment: Propagation kn rock layer for the appropriate distance,
This adjustment Increases with distance because vibration attenuates more slowly Iii rock than in the sail used as a bests for the reference curve.
• At -grade — Vh+iren corrsideringat-grade viEiratmr]rr ,raid, determine if the vibration ration efiararterestics are typical or efficient- Efficient FEDERAL TRAMIT ADNI NETfiATrpN IM
01-28
Cant..
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2561
RTC -732
Responses to Comments
TRANSIT NOISE AND VTBRATION IA'IPACT ASSESSMENT MANUAL
vibration propagation m alts .In vibration Levels approximately 10 dB higher than typical levels. This Fiore than doubles the potential trnpad zone for ground -borne vibration,
• Ground -Borne Propagation Ef ec1 — Coupling to 8ul$ding Foundation - Since annoyance from grour l -borne vibration and noise is an indoor pkenomerxwi, the effects of the building structure on the vibration must be considered. Woo -MI -we buildings, such as typical residential stnirtures, are more easily e'<cited by ground vibration than heavier buildings. in contrast, large masonry buildings with spread footings have a low resporxse to ground vibration.
Wheal a building foundation is d"arectly oil the rock layer, there is no coupling loss due w the weight and chillness of the building. Use the standard coupling factors based on building type if there is at least a le - foot layer of soil betweenthe building faurtdatkoru and the rock layer, 2c. Apply receivtx adjustments to the base curve using Table 6-13 and the descriptions below to acrt7urit bar the protect-spt cific receiver characteristics.
The data in Table 6-13 Is applicable wheir the building structural features are known.
For more generic cases that do not have Mailed Inforltration 4n individual buildings, use a conservative approach and apply tine following adjustments to predict indoor vibration based on the outdoor vibration, instead of using the adjustments in Table 6-13:i4-11.'",
• Light -weight, wood -Trine construction Ist floor: +3 to • Light -weight, wood -frame construction 2nd and 3rd floors: +6 dB • Large buildings: Ci dR
• Srrrafl masonry buildings: +3 dl3
Table 6-B Receiver Adjustment Factors for Generalized Predictions of G Vibration and (Noise Receiver
Factor
Ctdju€anent: to
Propagation Curve
Comment
Floor -to -floor
aunt aeon
I C8 5 floors
a ovr grad['
44 l l} floors
above nude
.2 riRai oar
- I riBPRoor
TINS factor accounts for dispersion and attenuation
of die vibration energy as it propagates through a
building starting with the first suspended Moor'
Amplification
due to
I,E$OirgnCE# tai
floors. walla
and oe_ilings
+y d8
Tho aortal amplification 'mil vary greatly depending
on the type of construction The amptiflcati'on is
lamer near the wallillaw and wail/ceiling
intersections.
Fbar-to An x nitarmati?n adivornenu for tI, first door assume a basement, FBDBe,r1 TRAMIT AL7MiNt5TRAT* N I-0'
01-28
Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2562
RTC -733
Responses to Comments
TRAPIFiIT NOISE AND lr8RAT1ON IMPACT ASSESSMENT MANUAL
In addruon to the comrnaits in Table 6-13, awe the fallowing guidelines to select the appropriate adlrxsttnentfactors, plate that receiver adjutments are add:Imo.. ▪ Vlbratcn generally reduces in level as tt propagates through a building.
As Indicated In Table 4-13, a I- to 2 -decibel attenuation per ilea• is typically appropriate,
+ Res+onaners of the building structure, particular Iy the floors. will cause some arnplification of the vibration. Consequently. fora wood -frame structure, the building -related adjustments nearly cancel out. Example! All adjustments for the first floor assuming basement arc -5 d$ for the coupling loss: -2 dB for the propagation from the basement to the dirt floor; and +6 r'aa for the llaor amplification. The total adjustment in this case is - I dR,
2d. Apply adjustments to the final *lusted curve using Table 6- I4 and the descriptions below t€r conven ground -b rrre vibration levels to ground -borne noise levels.
Table 6- I4 Conversion to Grrosind-berme Nolte
Conversion to Ground -borne Nolte
Peak frequency Df,grau,d 'Mi iSCir3tYl1:
US* these adjustments to estimate the A -
Low frequency d¢S0 Hz)
-SO dB
wiearglrted sound Ihv4I given the average
vlhraoon velocity level of the t*odtit suai;aes.
Leval iia
See tea ler guidelines for selecting kw -.Noise
dg q
Mid Frequency {peak JC to
bij Hz)
'33 d3
mud-. of alga-fresluerscy charatteriaocs_ Use
the high-Irequency adjarstrntirrtfor subway
tunnels In rock us if the dtbminant
l gh frequency I=•b{7 Hz)
-2G dB
Irflquendes of the vibration spectrum are
known TO bt• 6O I -It or greater.
Estimate the levels of radiated noise ling the average vibration amplitude of the room s.u-faces (floors, walls, and ceiling), and the total acoustical absorption In the room.
The urr-weighted sound pressure level is approximately 5 dgr37titr) less than the vibration velocity level when the velocity level is referenced to IxIO-t inchasIsee; but for a better estimate, it Is necessary to consider general frequency r'ariges. Since ground -borne noise is A.weighted. the adjustments rar'y by frequency r:uige, as described below. See Appendix U. I.4. I for more information on A -weighting,.
To select the apt apriate adjustment,. classify the frequency char -octet [sties. according to the guidelines Wow.
IFBI7kilAJ: TRAMIT ADMrNaSTRATtr}N I4
01-28
Cont.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2563
RTC -734
Responses to Comments
TRMSIT NOIRE AND l§BRATION II'1PACT ASSESSMENT MANUAL
■ Low Fr*qtitncy (<3t1 Hz) — Low -frequency vibration characteristics can be assumed four the Fall©warig corcliticons:
▪ Subways surrounded by etahesianfess sandy sail
• Vibration isolation track support systems
▪ Mot surface track
• Mid Frequency (peak 30 to 6D - z) — The mid -frequency vibration characteristic can be assumed for the following conditions:
• Subways. unless other information indicates that one of the other assumptions is appropriate,
▪ Surface track when the soil k very stiff with high clay content • High Frequency p.60 Hz) — High-frequexrcy characteristics can be assuned far the following conditions:
• Subways with the transit structure founded In rock
• Subway„ when there rs vary stiff, clayey soil
Step 3: Inventory of Vibration Impact
Take inventory orvtrra rn-sensitrhe /cad uses midi impact aid determine 1f a Detaisied Viib rkrn Analysis is required.
Compare the projected vibration levels. including all appropriate adjustments an Section 6.4, Step 2. to the criteria to determine ii lrnpact from ground -bone vibration or noise is likely, Mote -that for any transit mode, variation in vitiation levels under apparently similar wiii.htions iS riot uncommon. In the General Vibration Assessment, it is preferable to make a conservative assessment OF the impact and include buildings that may ultimately not be subject to Impact The standard curves in Section 6.4, Step I, represent the upper range of vibration levels tram well -maintained systems. Although actual levels fluctuate widely. it is rare that ground -borne vibration will exceed these curves by more than I or 2 dB unless there are extenuating circumstances such as wheel- or running -surface detects. However, because actual levels of mound-bcme vibration will s wnetirri differ substantially from the projections, use the fallowing guidelines to interpret vibration impact:
■ Projected vibration Is below the impact threshold - Vibration Impact is unlikely, and the environmental document should state this. • Projected ground -borne vibration is Q to 5 dB greater than the impact threshold - There is a strong chance that actual ground -borne vibration levels will be below the impact threshold. The erMronmenta1 document should report impact at these locations as exceeding the applicable threshold. present possible mitigation measures and costs, and ccrrnrnit to conducting more detailed studies to reline the vibration impact analysis during the ¢ngrieer-ing phase. During the Detailed Vibration Analysis. determine appropriate mitigation, if necessary. A site -specific Detailed Vibration Analysis may show that vibration impacts will not occur and control measures are not needed.
nDEtlAJ: T IT iWNIrNI5TRATrON I47
01-28
Cent_
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2564
RTC -735
Responses to Comments
TRANSIT NOISE AND V RATION IMPACT ASSESSMENT p1ANUAL
• Projected ground -borne vibration k 5 dB or greater titan the Impact threshold - Vibration impact is probable and Detailed Vibration Analysis must be conducted during the engineering phase to determine appropriate vibration control measures. The environmental document should report impact at these locations as exceedirg the applicable threshold, preant possible in itigatlon measures and costs, and commit to conducfirtg more detailed studies to refine the vibration impart analysis. during the engineering phase. During the Detailed Vibration Analysis. determine appropriate mitigation, id necessary. A site -specific, Detailed Vibration Analysis may show that very costly vibration mitigation must be Iruorporated into the project to eliminate the Impacrs.
ETA recommends the reporting of a vibration level as a single value and not as a range, as ranges tend to confuse the interpretation of impact - Express the results of the General Vibration ASsi strrent in mans of an inventory with the following components_
▪ Include all vibration -sensitive land uses as identified in the Vibration Screening Procedure.
• Organize the inventory according to the categories described in Table b-9_
■ Include irrformatnan on potentially feasible mitigation measures to reduce vibration to acceptable levels based on the generalized reduction estimates provided in this senator. To be considered feasible, the measure or combitratlon of measures must provide at least a 5 -dB reduction of the vibration levels and be reasonable in terms of cast.
These potential mitigation measures are considered preliminary. Final vibration mitigation measures can only be specified after a Detailed Vibration Analysis has been done; see Section 6.5 for more Indor iatlorr Vibration control k freq y -de endent; therefore, specific recommendations of vibration control measures can only be made after evaluating the frequency characteristics of the vibmion-
Example b -I General Vibration Assessment - LRT
General Vibratton Assessment tar an LR1" project
The hypaotherirai prulret era LRT xystem that opeeratm at 40 mph on artradee; ballast and be track wit's wrlderl rail. The first Boor of houses Is at Ili. ft from the LA T tracks and there is efficient propagation through the soil The: houses are constructed weth woreel frames: The holism will be. exposed to 26-0 train paYsshys per days Calculate the ground -borne vibration and assess for impact Select Rase CWrye for Ground Surrace Vibration
Determine the appropriate base curve and the RMg velocity level fd,YJ, According tat Table 6-9, the Rapid Transit sr Light Rail Vehicles curve k appropriate.
GS vela at Iii ft tar this curie at 50 mph
Apply Adjus [merits
Apply dee apprceprute sc,urce adltastmerrrss wing Trials 6.1 6. aDERAL TI AMIT fILDNI1INIMATION I4
01-28
Cc nt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2565
RTC -736
Responses to Comments
TIW4S T NOIRE AND Vt&RATION IA'1PACT ASSE SMENT I1ANUAL }p440
Source Speed Ad} tastment = 20 log t.5i1) = —1.9 µJ3
1,, = 65— 1,4 = X3,1 WcPf)
Apply the appropriate path adjustments using Table 6-I2 tffJit nt propa,yaiiun = .1,11 1,
Coupling tubuiltlin_y f uundaiJIM (Crowd rrum: 'r = —5iµ8 L,.=63.1+10-5=6tf.IG'iir5
Apply the appropriate receiver adjustments using Table 6.43.
Amp/ificahtlon dare iu resvnancre ul $Ithar = •h6 LIE
First flour attenuation = —1 aft
Ls,,=60.1+ii-2=72.11"riti
Assess for Impact
Because there are more than 70 events pet day, this project is in the Frequent Ewerws category (Table 6-2). For tategery 2 land 14S4. (reasdences) with frequent events• the impact c.iteria I. 72 VdE {Ta'61e 6 -ay Therefore. according to the fieneral Vibration Assessment there is potential for impact and a detailed Vibration Analysis €hould be completed,
6.5 Evaluate Impact' Detailed Vibration Analysis
Evaluate for import using the Detailed Vibration Analysis procedure, if appropriate (Section 6.I).
The goal of the Detailed Vibration Analysis is to use all available tools to develop accurate proFectians of potential ground -borne vibration impact and when necessary, to design mitigation measurek. A I]etailed Vibration Analysis requires developing aastlntates of the frequency components ad the vibration si oral, usually In terns of I/3 -octave -band spectra. The analytical techniques lot solving vibration problems are complex, and the technology continually advances. Therefore, the approach presented in this section focuses on the key steps for these analyses- The key elements of the petaled Vibration Analysis procedure and recommended steps are described below,
The methods in this section generally assume a steel-wheel/rail system. The procedures could be adapted to bus systems. However, this is rarely necessary because vibration impact it very Infrequent wltJi rubber -tired transit, In general, when situations arise that are not explicitly covered In the Detailed Vibration Analysis, professional pudgment may be used to extend these methods to cover these unique rte, when appropriate=_ Appendix G provides information on developing and wing non-standard modeling procedures.
Step I. Characterise Existing Vibration Conditions
Conduct measurements to surrey and doaiment the existing vibration conditions.
In contrast to raise Impact analysts, the existing ambient vibration is not required to assess vibration impact in most cases: but, It k important to sEDERAI TRANSIT ADN Nt5T 1.ATM}N hat?
01-2s
Cant_
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2566
RTC -737
Responses to Comments
TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL
der urrrent general background vibration In the protect corridor.. Because the existing envar•rinrnen al vibration is usually below human perception, a limited vibration survey is sufficient even fora moiled Vibration Analysis.
It is particularly valuable to survey vibration conditions at sensitive locations for the following reasolts
• To obtain rraluable itaftirrnatim on the true sensitivity of the activity to external vibration anti obtain a reference condition under which vibration is rat problematic.
■ To document that existing vibration leads are above or below the normal threshold of human perception for the existing condition, + To document levels of vibration created by existing raid limes. If vibration from an existing rail lime is higher than the proposed train, there may not be impact even if the standard impact criteria are exceeded. • To use existing vibration sources to €haracterize propagation.. Existing vibration sources such as freight trains, Industrial processes, quarrying operations, of normal traffic can be used to characterize vibration propagation. Carefully designed and performed measurements may eliminate the need for more complex propagation tests. See Appendix G for information on using non-slanderd modeling procedures. • To identify the potential for efficient vibration ration propagation. if a measurement the has existing vibration approaching the range of human perception (e.g., the maximum vibration velocity levels are greater than about 65 VdB), then this site should be carefully evaluated for the possibility of efficient vibration propagation.
Conduct measurements to characterize existing vibration conditions. The goal of most ambient vibration measurements is to characterize the rrns vertical vibration velocity level at the ground surface. In almost all rases, it is sufficient to measure only vertiml vibration and ignore the transverse components of the vibration. Although transverse tt]rnponentscill can transmkt vibration orgy into bulidi r , the vertical component typically dominatre.
I a. Choose Measurement Locations — Conduct outdoor err rigor indoor measurements to characterize existing vibration conditions, as appropriate, far the project- Although ground -borne vihauon is aim ost 'exclusively a problem inside buildings, it k generally reconnirrtard@d to perform measurements outdoors :because equipment inside the building may cause more vibration than exterior sources. Additionally, the building structure and the resonances of the building can have strong effects on the vibration that are difficult to predict It ca,n also be Important to measure and document those indoor sources o vibration. These indoor sources may cause './ibratiion greater than that due to external sources like street traffic or aircraft overflights. When measuring (indoor) floor vibration, take mea.siremenrs near the center of a floor span where the inbration amplitudes are the highest.
rfriEi AJ: TRAMIT ,aL7MiNt5TRATifaN I S4
01-28
Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2567
RTC -738
Responses to Comments
TRIV4SIT Nfl15£ AND l§BRATION It'1PACT ASSE SMENT I1ANUAL I b. Measurement Considerations
• Site selection — Selecarng sites for an ambient vtibratIc r 5rrvey requires mad lodgment. Sites sued to characterize a transit corridor shcxid be distributed along the entire project where potential for impacts have been identified and should be representative of the types of vibration environments found in the corridor. This would oommoniy include
o Measurements in quiet. residential areas removed from major traffic arterials to characterize low -ambient vibration areas; o MeanuremenLs along major tralik arterials and highways or freeways to characterize high -ambient vibration areas
• Measurements in any area with vi biatiorrr-sensidve activities; and • Measurements at any major existing source of vibration such as railroad lines.
• Transducer placement - Plane the transducers near the building setback line, For ambient measurements along railroad lines, it is recommended to include;
• Mukipie sites at several distances Prom the rail line at each site, and • 4 to f (y train passbys far each test
Because of the it i egufar schedule for freight trains and the low number of operations each day,, it is often impractical to perform tests at more than two or three sites along the rail line or to uteasur•e more than two or three passbys at each site.
Rail type and concktion strongly affect the vibration levels.
Consequently, it fa important to inspect the track to locate any switches, bad rail joints, Goss ugatioit, or rather factors that could be responsible for higher than normal vibration levels. Locations with these kinds of irregularities should he represented in addition to locations with rail in better condition.
• Transducer mounting methods - The way a transducer is mourned can affect the measured levels of ground -borne vibration. • Straightforward methods of mounting transducers an the ground surface or an pavement are adequate fat vertical vibration measurements for the Irrquericies of concern for ground -borne vibration (less than about 2001-Iajl.
o Quick -drying epoxy, day. or beeswax can be used to mount transducers to smooth paved surfaces or metal stakes driven into the gr vund.
• Rough concrete or rock surfaces require special mountings. Cue approach is to use a liberal base of epoxy to attach small aluminum blocks to the surface, and then mount the transducers on the aikiminum Nntks_
• When in doubn review the spenifiie tram -Anent donumenitation and discuss additional mourning guidance with the transducer manufacturer,
IFEDEilAJ: 'MAMA' ninniNt5TRAT* N 151
01-28
Cent
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2568
RTC -739
Responses to Comments
TRANSIT NOIRE AND VTBRATION It'1PACT ASSESSMENT i1ANUAL I c. Existing Yibratlbn C haractirlution — The appropriate methods of charat enring amba nt vibration are dependent on the type of Information required for the analysis. Consider the following when characterizing the existing vibration;
✓ Ambient vibratInn — Ambient vibration Is usually dtaratterized with a cnrctinuous I Q to 3f]-rrilnute measurement or vibration, The rims velocity level of the vibration velocity level over the measurement period provides an induction of the average vibration energy, The rrns velocity level over the measurement period is typically equivalent to a long averaging time ems Ievet
• Specific: events —Characterize specific events such as train passbys by the rens level over the time that the train passes by, If the locomotives produce vibration levels more than 5 dig higher than the passenger or freight cam obtain a Separate- rrrrs level for the iboorativin, The locomotives can usually be claiacterized by the Laaa drying the train paissby. The rms averaging time or time constant should be I ;second when determining La,... In some cater it may be adequate to characterize the tram passby whkh is simpler to obtainthan the rms averaged over the entire train pass*
■ Spectral analysis — Perform a spectral anaiy'sis of vibration propagation data_ For example, if vibration transmission of the ground is suspected of having particular frequency charactenstics, use I!3-tsctawe band charts to describe vibration behavior, Narrowband spectra also can be valuable, particularly for identifying discrete frequency components and designing specific mitigation measures.
Note that it is preferred to characterize existing vibration in terms b'l the ems velcrcrly level instead of the peak PK which is commonly used to monitor cvnstauctsen vibration As discussed in 5ecbon 5.1, nos velocity is Wnsidered more appropriate than PPY for deori#ring Fenian response to building vibration,
Step 2: Estimate Vibration Impact
Estimate ground -borne vibration clad noise at sites iW ere significant impact is probable and assess far ivrapoct.
Predicting ground -borne vibration =notated with a transportation profit continues to be a developing field. S+ cause ground -borne vibration is s complex phenomenon that is difficult to model and predict accurately, r iost projection procedures that have been used for transit projects rely o i empirical data.
The procedure rl rlbed in this section i bid on site -specific tests of vibration propagation. This procedure was devebbed under a FTA-funded research contracti52i and is recommended for detailed evaluations of ground - borne vibration. Other approaches to a prediction procedure, such as finite element methods, can be used. See Appendix C for information on using non- standard modeling procures_
FEDERAL TRANSIT ADMaNtST 1.ATION 157
01-28
Cont.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2569
RTC -740
Responses to Comments
TRMSIT NOISE AND l§BRATION It'1PACT ASSE SMENT r1ANUAL
OvervIrw of Fredlktinn Procedure — Thk procedure was developed to allow the use of data collected in one location to accurately predict vibration levels in another site where die geologic conditions may be completely different The procedure is based on transfer mobility. Transfer mobility is the complex velocity response produced by a point force as a funebort of frequency. it repsteeents the relatienshlp between a vibration source that excites the ground and the resulting vibration of the ground surface, It is a fraction of both frequency and distance from the source- The analyses in this manual focus on transfer mobility magnitude, which is the magnitude for the velocity relative m the forte without reference to phase_ The transfer mobility level is the level in decibels relative to I E-6 Iti+lts-x.
The transfer mobility measured at an esting transit system is used to normalize ground -borne vibration data ared remove the effects of geology, The normalized vibration is referred to es the force density. Fewte density is the force per root distance along the track in ibPitlf2. The force derrslty can be combined with transfer mobility measurements at viibiation-sensitive sites clang a new project to develop projections of futwe ground -bowie vileretien.
The transfer mobility between two points cor tpfeteIy defines the composite vibration propagation characteristics between the two points. In most practical cases, receivers areclose enough to the train tracks that the vibration cannot be considered as originating from a single point_ Therefore, the vibration source must he modeled as a erre-srwrce. Consequently, the point treader mobility must be modifled to account fora Ilne-source. The subsequent Ilne-source transfer mobility is given in units of decibels relative to I e-6 itrfsllbrrsgrt[ft}_ The prediction procedure considers gr«md-born vibration to be divided into several basic cornponerits described bellow and shown In Figure 6-5. • Excitation Force (Force Density) — The vibration enemy r€ rreeted by asdllatr ry and impulsive forces. Steel wheels rolling oil smWth steel rails create random oscillatory forces. When a wheel encounters a discontinuity such as a rail joint an impulsive force is created. The force excites the transit structure, etich as the subway tunnel or the ballast for at -grade Mack.
In the prediction methodd, the combination of the actual force generated at the wheeli'rail Interface and the vibration of the transit structure are usually combined foie an Moslem force density level_ The farce density revel is the level In decibels of the farce den icy relative to I' Ibfft'R and describes the force that excites the soillrock surrounding the transit structure.
• Vibration Propagation (Transfer Mobility) —The ribralio:n of the transit structure causes brate n waVEs Iii cite sail that prop away from the transit structure. The vibration energy cal, propagate through the soil or rock in a variety of wave forms. All ground vibration includes shear and compression waves. Rayleigh waves lad are also created and propagate along the ground surface. These Rayleigh waves Can be a F DERA1 TfRAMIT Al NI Nt5TRAT ON I 53
0 1-28
Cont.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2570
RTC -741
Responses to Comments
TRMSIT NOISE AND lrBRATION It'1PACT ASSE SMiENT I1ANUAL major carrier of vibration energy, The rnathenatl®I modeling of vibration is complicated when there are soil strata with different elastc properties. which is common. As indicated in figure 6-5, the propagation through the soillrock is modeled using the transfer mobility, which is usually determined experimentally,
The combination of tha force density level- and the transfer mobility Is used to predict the ground- surface vibration. This is the rnaior difference from the General Vibration Ass ment. which generalizes estimates of the ground -borne vibration.
• Building Vibration - When the ground vibration kites a building foundation. it sets the building into vibratory motion and vibration waves propagate throughout the building structure, The interaction between the ground and the foundation causes some reduction in vibration levels_ The amount of reduction is dependent on the mass and stiffness of the foundation. The more massive the foundation, the lower the response to ground vibration. As the vibration waves propagate through the building, they sin create vibration that can be feh and cause windows and household hold items to rattle_
• Audible Noise —In addition to vibration that can be felt. the vibration of room surfaces radiates Iow-frequPli y sound that may be audible. The sound- level Is affected by the amount of acoustical absorption in the reCelw9'
'____
iYYYi'r+ears )-
f$alm
ion R work ▪ \`
s-. 1'hnilun
imp, II: rn loran I.
pror>a0•t.,, It,rn:Ot
*Annah and Ya�dili
nnc1 n,t$nr IThJ'IdMlllla
c.[ILllort Fvrcr
Weed -a 6ensttyj
Wibrat.o,r Propnratvni
iTLnNar iota lllrri
HI tlfr j In,e,uamn
! -I Building VlMatrlan
Prega7ah_m- rhrrn.r}I'
innrnn7+hurlrIeu
Hadmon ad sound ar
N.C210+g rOcer, a.nar a
ivv+lal4al eY,rn774n^
In morn
*de*deb& Pte..
Figure 6-S Ground -Born Vibration and Noise Model
A fundamental assumption al - the prediction approach outlined In this section is that the farce density, transfer mobility, and the building coupling to the ground are all Independent factors. The fallowing equations are thea basis lot the nDERA1 PidAN IT ADNIIINIMATC.N I $a
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Ritz -Carlton Rancho Mirage MND 11942
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TRANSIT NOISE AND V RATION It1PACT ASSESSMENT I1ANUAL
prediction procedure, where all of the quantities are one-third octave bared spectral levels in decibels weak consistent reference values:
FLIL + LSTiti +
LA = LF + grnd + ILA^wt
where..
Lv
FDL
LSTM
�birrhi
LA
kraal
Eq, 6-5
Eq. 6=6
= ems vibration velocity level in Vdit
= foroe density level in dB for a het vibration source each ab a train
= line source transfer mobility level in dB from the tracks to the sensitive site
adiusttnenta in account for ground-bericS rg foundation Interaction and atrenuatlan or Abrasion, amplitudes as vibratloiv propagates through bi nbachess
= A•weigliotd SCUM level
= adlusuuena tit account for conversion fron ation sound pressure level inducing accounting tar the amount of acoustic J abbnn'prico inrfde the room, A Value of -5 dB ca17 be uieti for It ,e For typical residential roams when the decibel reference value for L is 1 micros In+sec01'O.1
= A weighingadjustrnent at the II3-octave band center frequency A11 of the quantities given above are functions of frequency, and the standard approach is to develop projections an a I1'3 -octave band basis using the aver values ferr each In -octave bard. The end results of the analysis are the DI - octave barns spectra of the grouted -borne vibration and the grourxk-borne noise_ The spectra are then •corrrpared to the vibration criteria for the Detailed Vibration Arnalysls, The A -weighted ground -borne noise bevel can be calculated from the vibration spectt urn and compared to the criteria. This more detailed approach differs from the feral Vibration A sessrient, where the overall vibration velocity level and A -weighted sound level are prericted without any consideration of the particular frequency characteristics of the propagation path.
The key steps In obtaining quantities foci' Eq. 6-5 and Eq. 6.6 are presented In the following steps and include;
Step 2a. Estimate force density
Step 2b. Measure the point source transfer mobility
Step 2c. Estimate line -source transfer mobility
Step 2d, Project ground -borne vibration and ground -berme noise 2a. Estimate Force Density ^ The estimate of force density can be based oai previous measurements or a special test program can be designed to measure the force dertsRty at an existing facility.
IF no suitable measurements are available_ conduct t,esting at a transit facility with equipment similar to the planned vehicles.. Adjustments for factors such as train speed. track support system, and vehicle suspension may be needed to match the force density to the conditions at a specific site, Review the report FEDERAL TMN IT ADMiNt5T1ATeON 155
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TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT 31ANUAL
"State -of- the Art Review: Prediction and Control of Ground -Berne Noise and Vibration from Rail Transit Trains" 1411 for examples of appropriate adjustments.
Force density is not a quantity that can be measured directly: it mart be inferred from measurements of transfer mobility and train vibration at the same site. To derive force density.. the best wits are achieved by deriwing line -source transfer mobility from a line of impacts. The standard appm r -h is to average the force density from measurements at three or more positions at came site. If feasible it is recommended to take me. stirertents at more than one site acrd at multiple speeds.
If no suitable measurements are available see Steps 2b and 2c for guidelines on obtaining line -source transfer mobility,
The farce density for each I13 -octave band is as fellows_ FDf, Lo — LSTM Eq. 6-7
where
PDL = fare density level In 46
Lr =measured train ground -borne Abrasion
level in Vd8
orm = lima -tourers transfer mobility teen! In d6
Figure 6-6 shows eisimple uracidaed force densities In decibels relative to I lb/tit) in. These ford densities were developed from measurements of vibration from heavy and LRT vehicles and represent an incoherent line of vibration force equal to the length of transit trains. This figure provides a comparison of the vJbratJon forces from heavy commuter trains and LRT vehicles with different types of primary suspensions, illustrating the range of vibration forces commonly experienced in a transit system. A force density of a vehicle includes the s araateeristics of its track support system at the measurement site Adlustmerrts must be applied to the force density to account for differences betwesn the facility where the farce density was measured and the new system being analyzed.
Figure 6-7 shows typical farce densities for rail transit vehicles at 40 mph on leafiest and the trades, which are approximately within the toieraric : shown in Figure 6-6. TIbe force densities should be applied very carefully far other track types and speeds. The embedded tracks, although considerably stiffer than ballast and tie v icks, are expected to show similar force density levels.!s3r The curves in Figure b-7 should also be applied with caution for newer generations of light rail vehicles as well as vehicles that utilize direct flxatioin racks.. The prefer -red approach for vibration predictions ',would be to perform force density meaurements at a systettl with ',chides and operations that are similar to those of the suture project.
nri6RA1 TRAMIT ADNIANt5TWATION 156
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?n
1D
ty
]1Z Gt
per
4c'
TRIV4SIT NOIRE AND VIBRATION IA'1PACT ASSE SMENT t1ANUAL I I
I I I
-, -1- —I r�
I I
Canarhar Rat Range
r,.arrnwrar Fiat Aram?,
- t-4 Rail Rana
Lip Rail kvangn
1 a3 Ociarra Band Center Fnsuunrcv. Hz
Figured -6 Typical Force Densities for Rail Tram it Vehicles, +I rmph Light Ralf. Average
ier BST Tiaras
-LrphI RWI Max Mir
SSTTrack.
Llp►rl Real MMrr '
BSTTracks.
31.S
113Octave Band Frequency, Hz
Figure 6-7 Typical Force Densities. for URT Vehicles, 40 rnph 2b. Measure Paint -Source Transfer Mobility — Using the appropriate instrumentation,measure point -source transfer mobility for sources with short lengths, such as buses or single car vehicles or cvolilmrts supporting elevated structures. Por longer vehicles, see Section sic for a discussion of ineasunrlg IIr- soiree transfer mobilities.
The test procedi.e to measure point -source transfer mobility consists of impacting the ground by dropping a heavy weight and measuring the force into the ground and the response at several distances from the Impact. Other excitation sours may Include swept sine, sine -dwell, random vibration. and maximum length sequence- The goal of thee test is to create vibration pulses that quiEtviL TRAMIT Al NI Nr5TRAT ON 157
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TRAP T NOIRE AND l§BRATION IA'1PACT ASSE SMENT 31ANUAL
travel from the source to the receiver using the same path that will he taken by the transit system vI bration.
Figure fri3 illustrates the field procedure for measuring both at•grade and subway testing of transfer nobility. A weight is dropped from a height a3 to 4 ft onto a force transducr_ The responses cif the farce and vibration transducers are recorded on a multichannel recorder for later analysis In the laboratory_ An alternative approach is to set up the analysis egtiprnent in the field and capture the signals directly, This complicates the field testing, but eliminates the laboratory analysis of recorded data_
At -Grade Testing
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Subway Testing
e grrssanamKars
Figure 6-5 Test Configuration for Measuring Transfer Mobility When the proriedure is applied to subways, the inrte must be located at the approximate depth of the subway. This is done by drilling a bore hole and locating the force transducer at the bottom of the bolt:. The tests are usually performed while the bore holes are drilled to allow for the use of the soil• sampling egrapment an the drill rig for the Li fer mobility testing. The force transducer k attached to the bottom of the drill string and lowered to the bottom of the hole. A standard soil sampling hammer is used to excite the ground: typically, a 144•pournd weight is dropped 1 El inches onto a collar that is attached to the drill string. The force transducer must be capable of opting under water if the water table is near the surface or a 5Iiwry drilling process is used.
Standard signal -processing techniques are used to determine the transfer function (frequency response !friction) between the exciting force and the resultant ground -borne vlhrdttori_ Numari€al reg,res±aon methods are used to combine a number rsf Two -point transfer functions Into a smooth point -source transfer mobility level that represents the average vibration propagation characteristic of a site as a fumittion of both distance from the source and FEDERAL 111,AMIT ADNI Na T .ATION I Sa
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TRMSIT NOIRE AND l§BRATION II'1PACT ASSE SMENT f1ANUAL
frequency, The transfer mobility level is usually expressed In terms of a groin of I f3 -octave band transfer mobility levels. Figure 4-9 Is an t eample of point - source transfer mobility levels from a series of tests at the Transportation Technology Center in Pueblo, Colorado,.kol nss saysr,
2n
H ]IA se
113 Datave Band Cemer Frequerry
125
250
F u►e I6W4 Example of Point -Source Transfer Mobility
Instrumnntatini
Performing a transfer inability test requires specialized equipment, which is generally available fram commercial Sorrces. Typical instrumentation foi fie1d- testing and laboratory analysis of transfer mobility is shown in Figure 6- I O.
A load cell can be used as the farce transducer. The farce transducer should be capable of impact loads of 5.030 to 50,0e0 pounds depending on the harnmer used for the impact, for borehole testing, the load cell must be hermetically sealed and capable of being used rot the bottom of a 30- to I00 -foot -deep bore partially filled wltfr water.
Either accelerometers or geophones can be used as the vibration transducers, Geophranes should be carefully mounted so that they are vertical. The requirement is that the transdiecers with the associated amplifiers he capable of accurately measuring levels of O000I Inlsec at 40 l -I and have a flat fiequarecy+ response from 6 Hz to CO Hz. Data should be acquired with a digital acquisitions system with a flat frequency response over the range ref 6 to 400 Hz FFD RAL TRAMIT ACrMiNI5TRAT*O'N
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TRAPt51T NOIRE AND VTBRAT)ON It'1PACT ASSE SMENT I1ANUAL ocogeri vreigmi
err
Tarilla Tranndumr
Foam Traci
Aereelerrome,'e
Field. Equ:ipmeni
Signal Gor (liming
and
Arnoltlltalinn
nOale:Aci ;itailicri
Srtiorr
Data iittosodion
Sp5renl
Laboratory Equipment
Farce Signal
Accoleddnelet 5agnala
+r7u-�iTIAI.[I
Spectrum
Amalrrar
Attet;onh]A
Strel
Irrlegrrrror
ee,,,ai
c�Ly
7Fcutrum
Wnrito&
co
"a'gnal Paoca55ng
SaiLWOR.
Figure 41-i 0 Equipment Required for Field Testing and Laboratory Analysis A itar -owband spectrum analyzer or signal -processing software cart be used to calculate the transfer luncthan and colrereriee between die force and vibration data The analyzer must be capable cif capturing impulses from at least two channels to calculate the fr sency'SpectrLarn of the transfer function between the force and vibration channels. Ail transfer functions should include the average of at least 20 impulses, Time averaging of the impulses will provide substantial signal enhancement, which Is usually required to accurately characterize the transfer frAlctip . Signal enhancement is particularly important when the vibration transducer is more than I 00 ft from the impIcL Alternative methods of determining transfer mobility may be used, provided that these techniques have been demonstrated to provide the same results as the conventional weight -drop method over the frequency range of 6 Hz to 400 Hr.. See Appendix G for information on developing and using non-standard procedures, These methods may include using other impulse -response measurement systems involving the use of shakers or electro-mechanical actuators, stimuli such aS sweeps or maximum length sequences f ). and various signal processing techniques_ A forthcoming ANSI Standard will describe in detail the procedures, methodologies, and reporting requlreinr?ntt for performing ground -borne vibration propagation measurements.
The transfer function can be calculated with either a spectrum analyzer or silted -processing software. Nate that transfer functions should include the ava,rage of at least 20 Impulses. Speclalaed multi -channel spectrum analyzers have built-in capabilities for computing trap fer functions and are computationally efficient. However. signal -processing software ran offer more FEl7ERAL TRANSIT ADNI NIS ATION Id0
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TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL
flexibility in analyzing data signals and allows the use of different digital signal processing methods. Typliail measurement programs Involve acquisition of data in the held and later processing of the information in a laboratory. However-, recent advances in instrumentation and signal -processing software allow data to be collected and analyzed while in the field,
2c. Estimate Line —Source Transfer Mobility — Estimate line -source transfer mobility for long sources such as multi -car trains. Line -source trsfer mobilities are used to norm Irze mitred vibration velocity levels frorn train passbys arid to obtain force density. Two different appraadw-s can be used to develop estimates of line -source tramfa~ rnobrlity_ The forst consists of using limes or transducers and the second consists of a line of Impact positions.
Option A: Lines of Transducers — Develop line -sauce tr nsfer mobility curves from tests using one or more lines of transducers as shown in Figure 6 -II and described below_
Narrowbsnd Transfer Mpbi lity
t i"d Octarr Bind inmost Mobility
Dna space -we tar earn nistance al uses. anal
bait Gurus ofTransirr Mobil illy
as a Futreikm of Distance
isms hit each c clavo- Iaar.i
Lim -ileum* Trans let Mobility
4sahmried using n n flrisar n+tsyrstssi
a loom u 1In74, D1.41.11 rrratylilyJ
FIv4uarWt
• e } -aer� Ltrre
•
-
sou ae
gnet
Figure 6-I I Analysis or Transfer Mabllley
AL Obtain the narrowband transfer function between source and recoalver all each rneasurc'rn-rent,position There should be a minimum of four distances in any test line. Because of the possibility of Iocal variations in propagation characteristics. two Dr more lines should be used to characterize a site d possible. A total of I0 to 20transducer positions are often tiled to characterise a site.
Aii. Calculate the equivalent IJ3-octave baled transfer functions, generally between 6 and 44(1 Hz. This reduces each spectrum ho 15 numbers_ As shown in Figure 6-I I the 1ii3-octave band spectrum is much smoother than the narrewtrand spectrum,
Calculate a best -lit curve of transfer mobility as a function of distance for each 1I3 - tae brand. When analytirg a spent -lc site. the best -fit curve will be FEDERAL TRANSIT ADN NtST 1.ATkrni Ib I
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TRIV4SIT NOIRE AND l§BRATION IMPACT ASSE SMENT I1ANUAL
based on IO to 20 points. lJp to several hundred paints could be used to determine average best -fit curves for a number of silt, Air. Apply the best -fit curve to the vibration sources. The I f3 -octave band best -fit curves earn be directly applied to point vibration sources. Buses can usually be considered point -sourc=es. as can columns supporting elevated structures. However, for a line vibration source such as a train. numerical integration must be used to calculate the 'equivalent lime -source transfer mobility.The numerical integration procedures are detailed in the TRB publication. "A Prediction Procedure far Rail Transportation Ground -Alarm - Noise and Vibration,"ilo
Option B: Line of impulses — This Second procedure for estimating tine. source transfer mobility is be for detailed .assessment of specific vibration, paths or specific buildings and is a more direct approach..
Bi. Measure multiple point -source transfer mobilities according to the procedures in Step 2b above, The vibration transducers are placed at specific points of interest aril a line of impacts is u€ed. For e,+ miller a 154 -flat train might be represented by a line of i I Impact positions along the track centerline at IS -foot intervals (Figure 6- I2).
BII. Same the point -souse results using Simpsons ruler for numerical integration to calculate the line -source transfer mobility.
Figure 6-13 shows an example of line -tea -€e transfer mobilities that were tli raved from the point -source transfer mobilities shown in Figure 6-9.
Figure 6.1Z Schematic of Transfer Mobility Measurements Using a',Line of Impact °• Simpson't. role k a msthrd for apprnxlmmtlt rag Imegrals F DERAL TRAMIT ADNIrNt5TRATION I
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TRAPIFiIT NOIRE AND Vt&RATION I€'1PACT ASSE SMENT MANUAL 9 LB 71.5 4'I
1/3 Octavo Eland Ginter Frequency. Hz
17f
Figure a -I Example of Lire -source Transfer MoblUey
2d. Project Ground -Borne Vibration and Noise — Combine force density and line -source transfer mob Iity to protect ound-I rrte vibration. Tries. apply adjustment factors to estimate the building response €n the ground -borne vibration and to estimate she ,bl-weighted sound level inside buildings.
The propagation of vibration from the btdldirg foundation to the receiver room is very complex and dependent on the specific design of the building. Detailed evaluation of the vibration propagation would require extensive use of numerical procedures such as the finite element method. Such a detailed evaluation is generally not practical for individual buildings considered in this manual. If the detailed features of the fndIvidual b ulldiirgs are available, the recommended procedure is to imtimate the propagation of vibration through a building and the radiation of sound by vibrating building surfaces using simple empirical or theoretical models. The recommended procedures are outlined in the handbook of Urban Rail Noise aad Vibration ControVfi The approach consists of adding the fallowin u;trr, .its to the I/ -octave band spectrum of the projected ground -borne vibration:
• Building response or couprmg loss - This adjustment represents the change In the incident ground -borne vibration due to the presence or the hulloing foundation. the adjustments described in the handbook 1*a are shown In Figure 6-I4. Note that the correction Is zero when estimating basement floor vibration or vibration of atirade slabs.
Measured dues may be used in place of these generic adjustments. • Transmission through the building - The vibration amplitude typically deer € si as the vibration energy pr opagata- from the foundation thronagh the remainder of the building. The general assxnption is that vibration attenuates by I to 2 dB for each floor. • Floor resonances — Vibration amplitudes will be amplified because of resonances of the flt orfceiling systems. Fora typical wood -frame FEEJERAL HERMIT ADNIaNtTTfaATn3N I 6 3
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TRIV4SIT NOIRE AND lrBRATION IA'1PACT ASSE SMENT MANUAL residential structure, the fundamental resonance s usually In the 15 to 20 Hz range_ Reinforced -concrete slab Koons on modern buildings will have fundamental resonance frequencies in the 20 to 30 Hz range. An amplification resulting in pan of app -t ximately 6 dB should be used in the frequency range of the fundamental resonance,
• Floor vibration and ground -borne noisy, — The projected Boor vibration is used to estimate the levels of ground -borne noise. The primary factors affecting noise level are the aver 4I4ti vibration level of the room surface# and the amount of acoustical absorption within the room. The radiation adjustment is -5 d8 for typical rooms, car 001 whleh gives,
where
rr�-Wr
LL,+ —5
Eq. 6.1
= A -weighted sound lever in a I/a-octave band
= rills vibration velocity level is that band
= A-weighti:eg adjustment at the I13 -octave band center rr equenzy
The A -weighted Ieveds in the 1/3 -octave bands are combined is produce the overall A -weighted sourd lead,
10 u
rc
Bs
•tp
3 -2J
— lawny &Ird1�, m Pins.
e �,. Ixp?MWFrIrY&ram m Spraed Food ism
_.a,.._ 6mgte name, Ilaerienitnl
.,—.. I in } Sias' ned:1e,n1a1
... -,.. F m a Ginn/ Mezanry llmI1q on Sorand
JJ 31 5 C 9
t �3 Ottin8 Beuid Crlfltir FiliquallCy. M2
FRgurc 6-14 Foundation Responses for Various Txpss of Buildings 250
Where detailed information on the structural features of individual buildings arcs unavailable and there are no site -specific data on outdoor to indoor propagation characteristics. the preferred approach is to apply a combined factor for the fecundation response and the gain from Iloor re oriartces. Empirical data based on the TCRP D-12 Project from 34 measurement sites across 5 Cities In North FEDERAL TRANSIT ADN NIsrPATrf3N Iva
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TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL
Airier Ica and other studios suggest that the average charge In vibration from outdoor to indoor was it d$ across all I13 -octave bands with a standard deviation of approximately 5 to 6 da in the 31 to 63 I-lz frequency,rmaotr Therefore, the recommended approach for predicting indoor vibration based on outdoor data is to use an adjustment of +3 to +6 dB for lightweight, wood - frame construction and use an adjustment of €i dI3 for heavier buildings, However. for buildings with high -vibration sensitivity or where there is concern regarding interference with vibration -sensitive ecfi,flprnent, it is advisable to measure the outdoor -Indoor response of the building, using the proms described in motion 2b or 2.c, to determine the actual response of the foundation and building to vibration.
Step 3: Assess Vibration impact
Take rirventory of vlbretron-sensitive krnd uses with itrrpat£r..
Assess vlbratkm Impact et each receiver of interest using the impact critesrfa in Section 6.3. Note that ground -borne vibration arid noise levels that ibcceeded criteria in the General Vibration Assessment may not at impact according to the more derailed procedures of the Detailed Vibration Analysis; in which case. mitigation is riot required- eat if projected levels still excr d the crited a, evaluate vibration mitigation measures using the SpeCtra provided by the DetailedVibration Analysis,
Step 4: Determine Vibration Mitigation Measures
Select proctcarl vibration cone ref measures that wifi be effective at the dominant vibration frequencies and c mpotlite with the given transit structure and tra,d4 support system
The pin pose of vibration mitigation b to minimize the adverse effects that the project ground -borne vibration and gr u rid -borne anise will have on sensitive land uses. Because ground -borne vibration is not as common a problem as etwircnmerital noise. the mitigation approaches have riot been as well defined. In tnnte camas it may be necessary to devidep Innovative approaches to control the impact. See Appendix G for infrrnation on ring non-standard methods.
Standard vibration control measures for rail transit systems are discussed In this step, Note that vibration control measures for rail transit systems are riot always effective for freight traiia.0w) Cus systems rarely cause vibration impact, but if impact occurs, roadway roughness or unevenr 'caused by bumps. pot holes, expansion points, or driveway transitions are usually the causes.
Smoothing the roadway surface b typically the recommended course of actlon.t r
The Heavy DIEbade asaodated with freight rail are outside the ravage of applrcabre design pawrierers for vibration reduction on Ilghrer hall transit systcrirs. Plans to rrlcaeaat txkrais raictad tryt s ckaaer vibralioh•sttrartfre sites in order tat. accommodate a row rai tr iris t lint in 04 ROW moot be earuhdly conairhtrcd busiwr it may not ha penal* to rnitg*. the Increased vitration Inipara from freight trains.
In canes where arwbber-tired system rums Inside a building such as an airport peopie mover. vibration control may invoke additional roeasls+es. Laidirig and unioadir% dguidewtsy support &rams tnar genera:a dynamic fortes Asa t a mrnit. into the building structure. Spaci>'J g,rideway sapport to ems mar Ito r4grir4nit sii r to ilia discussion below !r garding Heating silks.
FEDERAL TRANSIT ADM1NISrRATION I65
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TRANSIT NOIRE AND l§BRATiON IA'1PACT ASSE SMENT I1ANUAL Vibration redurtiin measures incur additional costs to a system_ Some of the same: treatments for noise mitigation can be considered for vibration mitigation.
Casts for nose control measures are documented in a report from the Transit Cooperative Research Pi ugran (TCRP} »YW 1iere applicable to vibration reduction, costs for noise abatement meth from that report are given in the following sections, These costa reflect the noise mitigation casts as of I9'57 {unless otherwise noted}, and should only be used as representative estimates when considering noise mid y rion options. Current noise mitigation casts should be researched before decisions on noise mitigation options are finalized, and then they should be documented according Et} Section $.
Mitigation of vibration impacts may invohfe treatments at the source, along the source -to -receiver propagation path. or at the receiver, Ia. Evaluate Source Treatments - The most diective vibration mitigation treatments are applied at the vibration source- This is the preferred approach to mitigation when possible. Possible source treatments include • Preventative Maintenance — Effective maintenance programs are essential for controlling ground -borne vlticatIcan. Key vibration points are discussed blow: see Section 4.3, Step 7 for more detailed infonmadon on the benefits of effective maintenance programs on controlling transit noise and vibration. Mille these are not mitigation measurers in the traditional sense and should not be included as mitigation in an environmental document they can hrelp to keep both noise and vibration Ie+els at a "like -new" level or reduce both in systems with deferred maintenance_
• Rail grinding is a partieulaiiy important practice for vibration mitigation for rail that develops corrugations. The TCRP report rioter that periodic rail grinding rsults net savings per year CHI wltieel and rail wear. Most transit systems 'Contract out rail grinding, although some of the larger systems make the investment and da their own grinding. as mentioned in Section 4,5, Step 7. the typical rail grinding cost would be $1000 to $7040 pet grinding pass mile with an additional investment of approximately $I million Inr the equipment for a larger transit system to do its own grinding. • Dramatic vibration reduction results can be achieved by removing wheel flats t1UQugh wheel truing. As mentioned in Section 4.5. Step 7, a wheel truing machine costs approximately $ I million, including associated maintenance: materials, and labor costs.
The TCRP report figures a system with 740 vehicles would incur a yearly cost of $304,000 to $400,000 for a wheel truing program - • Profile grinding of the rail head in combination with a wheel ming program may be the most practical approach to controlling and reducing vibration and noise where such practices are not normally conducted_ Profiles should be defined during the design phase and should be iii place when system epitts ib4 The cost of FEpEaaa TRANSIT AlaMiNtgraaTrON 166
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Responses to Comments
TRAPISIT NOIRE AND l§BRATION It'1PACT ASSE SMENT I1ANUAL wheel and rail profile matching may be incorporated In the crew vehicle and new roll costs_
Rough wheels or rails can increase vibration levels by as much as 20, dB in extreme cases, negating the effects of even the most effective vibration control measures. Yet, It Is rare that vibration control rraaa cu es {such as those discussed below) will provide more than 15 to 20 dB attenuation. When there are ground-bolme w ibration impacts with existing trait it equipment. the hest vibration control measure often Is to Implement new or improved maintenance procedures_ Grinding rough nr corrugated rail arm wheel truing to eliminate wheel fiats and restore the wheel. contour may provide considerable vibration reduction. Regular maintenance may replace the rieed to modify the existing track system, such as through adding floating slabs.
▪ Planning and Design of Spec/Id Trackwork — A large percentage of the vibration impact from a new transit facility is often caused by wheel impacts at special traclrwork for turnouts acrd crossovers. When feasible, the most effective vibration control measure k to relocate the special tr ckwork to a less vibration -sensitive area- This may require adjusting the location by several hundred feet provided it will not have an adverse impact on the operation plan for the system, Careful review of crossover and turnout locaticins during the protect development plias is an important step to minimizing potential for vibration impact.
Another approach is to use special devices (frogs) at turnouts and crossovers that incorporate titca-hanions 8o close thegaps between running rails. Frogs with sptirtg-loaded mechanisms and frogs with movable points can substantially reduce vibration levels near crossovers.
According to die TCRP report, a spring frog cents about Si 2,000, twice the cost of a standard frog. A movable point Frog involves elaborate signal and Gortlirol circuitry resulting in higher casts at approximately $200,000,
• Vehicle Specificat Qrxs — The ideal rail vehicle with respect to minimizing ground —borne vibration should have doe following characteristics'
P Low, unsprung weight
• Soft Omar/ suspension
o A minimum of metal -to -metal contact between moving parts of the truck
• Smooth wheels that are perfectly round
A limit for the vertical ronance frequency of the primary suspension should be included In the speclfrcatinns for any new vehicle_ A vertical resor once frequency of I2 Hz or less is suffiolerrt to eetrttrmf the levels of groLeld•borne vibration. although some have recommended the vertical resonance frequency be less than B i+z.
;WW1. TRAMIT atamiNt5TWATrr3N 147
01-28
Cant_
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2584
RTC -755
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TRAP T NOIRE AND l§BRATION It'1PACT ASSESSMENT MANUAL
• Spacial Track Support Systems — When the vibration assessment Indicates that vibration levels will be excesive, the track support system is typically rmxhfied to reduce the vibration ievek,
Floating slabs, resiliently supported ties, high-resilierice fasteners, and ballast mats can be used to reduce the levels of ground -bowie vibration.
To he effective, all of these measures must be optlmared for the frequency spectrum of the Oblation. Most of these relatively standard procedures have been successfully used on several subway projects, Applhgtions on at -grade and elevated track are I ass common. This is because vibration Impact less common for zit -grade awl elevated track, Note that the cost of these types €af vibration control measures is a. highly percentage of the overall construction costs for at -grade and elevated track, and ovestre to the elemortts can require substarmtral design rT,odlfii 1 rrs.
Each major vibration control measure for tract support is discussed below, Costs for these treatments are trot revered by the TCRP report, brit are given as estimates based oh transit agency e)perJence. • Resilient fasteners — Resilient fasteners are Wad to fasten the rail to concrete track slabs, Standard resilient fasteners are very stiff In the veil: cal direction, usually in the range of 200.000 Him, and do provide some vibration reduction compared to the rlgJd fastening systems used on older systems (e;g„ wood half - ties embedded in concrete).
Special fasteners with vertical stlffness in the range tit 30,000 Ibfin may reduce vibration by as couch as 5 to 10 dB at frequencies above 30 to 40 Hz. These premium fasteners vary in coast and be priced svmpetitively when purchased in large quantities.
• Ballast mats - A ballast mat consists of a rubber- or other type of elastrrneer pad that is placed under the ballast. In general, the mat must be placed on a corm ere pad to be effective They will not be as effective if placed directly on the soil or the sub - ballast. Consequently, most ballast mat applications are in subway or elevated structures.
Ballast mats can provide B to 12 dB attentataon at frequencies above 25 to 30 I-I.z,sg,. Ballast mats are often agcad retrofit measure for existing tie -and -ballast track where there is vibration impact, Installed ballast mats cat approximately $ I00 per track -toot.
• Undertie pads - Undertie path (resiliently supported
concrete ties) consist of a rubber pad mounted on the bottom of a concrete tie directly on the ballast. The pads provide vibration isolation at frequencies above 25 H`3 acrd are easy to FEDERAL TRANSIT ADNIiNt5Tf1ATM3hl I r, W
01-28
Cont,
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2585
RTC -756
Responses to Comments
TRMSIT NOISE AND 1c8RAT)ON IMPACT ASSESSMENT I1ANUAL
wnstail or retrofit. Installed uralertle pads cost approxrrnately $260 per trade -loot_
• Resiliently supported ties - The resiliently supported tie sysdern consists of concrete ties supported by rubber pads resting on top of a slab trade. or subway Invert. The rails are fastened directly to the concrete ties using standard rail clips_ Resiliently supported rats provide vibration reduction in between 15 to 40 Ha, which is particularly appropriate for transit systems with vibration impact in the 20 to 20 Ha range..
A resiliently supported tie system casts approximately $400 per track -foot
• Floating slabs - Floating slabs can be very effective at controlling ground -borne vibration and noise and consist of a concrete slab supported on resilient elements. such as rubber or a sumilar elastomer, Floating slabs are effective at frequencies greater than their single-de.gree-cif fr,eedorn vertical resonance iremrency.
Floating slabs ate among the most es aerisiv+e vibration control treatments. A typical double -tie floating slab systern costs approximately 4 times the cost of ballast and tie per track font.
Examples of floating slabs Include:
- Floating slabs used in Washington, DC Atlanta, and
Boston, I' IA were all designed to have a vertical
l
resonance. in the 14 to I7 Ha range -
- A special system referred to as the double -tie system was first used on Toronto. It consists of 5 -Total I©ng slabs with four or more rubber pads under each stab.
This system was designed with a r>asortance frequency in the 12 to 16 Ha r ng3.
Another special floating slab was used in San Francisco's Bay Area Rapid Transit (BART) system. It uses a
descontinirous precast concrete double -tie system with resonance frequency in the 5 to 14 Hz frequency
rang
• Tire -derived aggregate (T0NI,— TDA (shredded tires). consists of a layer of tire shreds wrapped in geotech fabric placed underneath the ballast a n hard packed ground. This is a new, low- cost option that can provide reduction in vibration levels at frequencies above 25 Hz, This mitigation measure has proven to be effective for the Denver Regional Transportation District I(RTDI light rail system as well as the Santa Clara Valley Transportation Authority 0/TA) Tight rail systern:591 but the effective IiFe of TDA has riot .been determined. Installed T1DA costs approximately $,2b(} per track -foot
• Other t1-eatroents — Changing any feature of the track support system can change the levels of ground -borne vibration_ Approaches FEDERAL PRAMIT ADNIiNIITF1ATM3N It.7
01-28
Cant.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2586
RTC -757
Responses to Comments
TRIV4SIT NOISE AND l§BRATION It'1PACT ASSESSMENT I1ANUAL such as using heavier rail, thicker ballast,. err heavier ties can be expected to reduce the vibration levels_ There also is some Incication that vibration levels are bwer with wood ties compared to concrete ties. But there is little confirmation that any of these approaches will make a substantial cliairgC in the vibration levels, ■ Operational Changes - The mast effective oper-ational thange k to reduce the vehicle speed. Reducing the train speed by a factor of two will reduce vibration levels approximately 6 dB. Other opefational charig include:
• rise of equipment that generates the lowest vibration levels during the nighttime hours when people are most sensitive to vibration and noise,
▪ kip -wing nighttime schedules to minimize movements in the most sensitive hours.
While there are tangible mitigation benefits from speed reductions and limits on operations Awing the most sensitive time periods,'FTA does not generally accepit speed reduction as a vibration mitigation measure for two Important reasons_ ( I ) speed reuct►an is unenforceable and negated if vehicle operators do not adhere to established policies, and (2) it is contrary to the purpose of the transit investment by FTA,. whidi is to move as many people as possible as effiiently and safely as possible- FTA does not recommend limits On operations as a way to r edrite vitrratiori impacts.
I b. Evaluate Path Treatments -'When vibration mitigation treatments canrxat be applied at the vibration Source or adtfitinnal mitigation is required after treating the source. the next preferred placement of vibration mitigation is along the vibration propagation path between the source and receiver. Possible patty treatments Include:
• Trenches - Use of trenches to control ground -borne vibration is analogous to controlling airborne noise with noise barriers- This approach has not received much attention in the United States, but trenches could be a practical method for controlling transit vibration from at -grade track, A rule -of -thumb gw n by Richert and Hall(00 is that iF the trench Is located close to the source, the trench, bottom muse be at least d.6 times the Rayleigh wavelength below tine vibration source, For most soils, Rayleigh waves travel at around 600 fusee. which means that the wavelength at 30 Hz is 20 ft requiring that a trench be approximately IS ft deep to be effective at 30 Ha,
A trench tan be affective as a vibration barrier if it is either opmi or solid. The Toronto Transit Commission tested a trench filled with Styrofoam to keep it open and reported successful performance over a period of at least one year. Solid barriers cam be constructed with sheet poling or coocrett poured into a trench_
• Buffer Zones — Expanding the +ail ROW can be the most economical method of reducing the vibration impact by simply incre-asireg the distance between the source and receiver_ A similar app -math k to atiERAL PRAN IT ADMiNt5Tf1ATIQN I V
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Cant.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2587
RTC -758
Responses to Comments
TRAP T NOIRE AND l§BRATION IA'1PACT ASSE SMENT i1ANUAL
negotiate a vibration easement from the affected property owners je-g-
a row of 514e -family homes adjacent to a proposed commuter rail line). There may be legal limitations, however, on the ability of funding agencies to acquire land strictly for the purpose of mitigating vibration (or noise) impact.
Ic Evaluate Deceiver Treatments — When vibration mitigation treatments cannot be applied at the source or along, the propagation path, or if combinations of treatments are required treatments to the receivers can be considered as described bellow.
• Rullding Modifications — In some eirrt.wrrnrancim It Is practical to modify the affected building to reduce the vibration level. Vibration isolation of buildings consists of supporting the building foundation on eiastomer pads, similar to bridge bearing pads, Vibration isolation of buildings k seldom an option for existing buildings and Is typically only passible for new construction. Vibration impacts or, sensitive laboratory instruments, such as electron microscopes, may be controlled with vibration isolation tableA..
This approach Is particularly important for shied -use facilities such as an Alice space above a transit station or terminal, When vibratkm- setuiaive equipment such as electron microscopes will be affected by bransit vibration specific miidil"r;atians to the building structure may be the most cost-effective method of controlling the Impact aside from modification of equipment mounting systems. For example, the floor upon which the vibration -sensitive equipment is located could be stiffened and isolated from the remainder of the bidding to reduce the vibration_ Alternatively, the equipment mourning systems could be modified or the equipment could be relocated to a different building at far less cost.
laDERAL TRAMIT AtimiNt5TRATafyN III
01-28
Cint.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2588
RTC -759
Responses to Comments
TRANSIT NOIRE AND l§BRATION It'1PACT ASSE SMENT f1ANUAL SECTION Noise and Vibration during
Construction
Construction noise and vibration often generates complaints from the €omrnui sty, even when constructic i Is fora limited timefrarne. Public concerns about construction noise and vibration increase considerably with lengthy periods of heavy construction on major projects as well as prevalence of nighttime construction (rafter' scheduled to avoid disrupting workday roadand rail traffic). Noise and vibration complaints typically arise from Interference with people's activities, especially when the adjacent community has no clear understanding of the extent or duration of the corrstnsction Misunderstandings Carr arise when the community thinks a contractor is being iruerrsitJve, and the contractor believes it Is performing the work In compliance with load ordinarices. This situation underscores the need for early identification and assessment of potential problem areas.
This section autllries the procedures for assessing noise and vibrations Impacts during construction. The type of assessment.(qualitative or quantitative) and the level of analysis are determined based on the scale of the project and surrounding land uses. In cases where a full quaiatitative assessment is not warranted. a qualitative assessment of the construction wise and vibration environment can lead to greater understanding and tolerance in the community.
For major projects with extended periods of construction at specific locations, a quantitative assessment can aid contractors in making bids by allowing changes in construction approach acrd including mitigation cots before the construction plans are finaltied-
Generally, local noise ordir>a.icm are not very useful for evaluating coristruction noise impact. They usually relate to rnisarr€+e and hogs of allowed activity, and sometimes specify limits in terms of maximum levels, but are generally riot practical for assessing the impact of a construction protect- Project construction noise criteria should take Into account the existing noise environment. the absolute noise levels during constniction activities, the duration of the constriction, and the adjacent land uses. While it is not the purpose of this marital to specify slawfard zed criteria for construction noise iniipact, the following guidelines can be considered reasonable crltea-ia far assessment If these criteria are exceeded„ there may be adverse community reaction.
Procedures for assessing construction noise are presented to Section 7, I.
Procedures for assgiceing construction vibration are presented in Section 7,1
7.1 Construction Noise Assessment
Noise Impacts from tonstrrrCtion may vary greatly depending on the duration and complexity of the project The key elernertts of the Construction Neese Assessment procedure and recommended workflow are as follows, F DERAL TII,AN IT ADMiNr5TRATif3N In
01-28
Cc nt
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2589
RTC -760
Responses to Comments
TRANSIT NOIRE AND l§BRATION It'1PACT ASSE SMENT I1ANUAL Step I : Determine Level of Construction Noise Assamsrnent Step 2: Use a @ualitative Construction Nose Assessment to Estimate Construction Noise
Step 3: Use a Q i titetave Construction Noise Assessment to Estimate Construction Noise
Step 4: Assess Construction Noise Impact
Step 5: Determine Contvuctyan Noise Mitigation Ileasuran If there is Uriee tainty in how to determine the appropriate level of assessment, contact the ETA Regional Aim,
Step I; Determine Level of Construction Noise
Assessment
c1etenrine the approip note fine) of assessment batted ran the scale and type oldie profert Land depending on the stage of enrironmentai rt'at'rew Consider the following factors:
• Scale of the project
• Proximity of noise -sensitive sites to the construction zones • Number of noise -sensitive receivers in the project area • Duration of construction activities aiear noise-serwsiLI receivers • Schedule, inclining the construction days. hours, and time periods • Method (e.g„ cut -arid -cover vs. bored tunneling)
• Concern about construction noise expressed in comments by the general public (eg.. through scoping or public m tkr s) I a. Determine if an assessment k required Construction Noise Assessments are not required for many small prolerts including • Installation of safety features like grade -crossing signals:
• Track improvements within the ROW: or
• Erecting warnII buildings and faolittiies which are similar in scale to the surrounding deuelgpneent.
For small profits like these, include descriptions in the envlrarrriental document oI the length of comb uctiorn, the loudest equipment to be used, the expected truck access rotates the avoidance of nighttime activity; and any other relevant planned construrtion method.
I b, Determine whether a qualitative or quantitative assessment required
• Qualitative Construction Noise Awss+essr It —Qualitative Construction Noise Assessments may be required fax projects with less than a month of construction time in a noise -sensitive area. See Step 2 for more information on Qualitative Construction Noise Assessments aDERAL TRAMIT ittitetNISTRATii3N 173
01-28
Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2590
RTC -761
Responses to Comments
TRMSIT NOIRE AND l§BRATION It'1PACT ASSESSMENT t1ANUAL
• Quantitative Construction Noise Assessments - QuantiI3dve Construction Noise Assessments may be required for prole€ts with a month or more of construction in noise•sensitive areas or if particularly noisy equipment will be involved, See Step 3 for more information on Quantitative uctlon f*loi:se Assessments_
Step 2: Use a Qualitative Construction Noise Assessment to Estimate Construsti€an Noise
Use n garatilattive construction ruse assessment to estimate construction noise four appropriate protect per Section 7 f, Step I b.
Provide qualitative descrIptrtans in the envtronmer rtal dcicaanent of the following elements.
• Duration of construction (both overall and at specific locations) • Equipment expected to be used (e.g, noislgnt equipment) • Schedule with Inuits on tirnes of operation (e.g, daytime use only) • Monitoring of noise
• Forum for communicating with the pulblic
• Commitments to limit noise levels to certain levels, including any local ordltmntes that apply
• Consideration of ariplicatlnra of nots.e control treatments used successfully in other projects
Effective community outreach and motions are important for these projects.
Disseminate Ir formation to the public early regarding the kinds of construction equipment, expected noise levels, and durations to forewarn potentially affected neighbors about the temporary inconvenience. Including a general description of the variation CI noise levels during a typical construction day may also be helpful.
Note that the construction criteria in Step 4 do not apply to qualitative assessments,
Step 3t Use a Quantitative Construction Noise Assessment to Estimate Construction Noise
Use a qu ntita tine construction nuke assessment to estimate construction noise fu uppraprlate projects per Scilicet 7. I, Slop lib.
For Quantitative Construction Noise ,assessments, fvilow the recommended procedure in this step and Include a description of the planned construction mettrads and any basic measures that have been identkiled to reduce the potential impact, mach as prohibiting the noisiest construction activities durlarg the nighttime. in the environmental document. It may be prudenrt, however. to defer final decisions on noise control measures until the project and construction platys are defined in greater detail during the engineering phae. • Noise Source Levels from Typical Construction Equipment and Operations —The noise levels generated by corlstructitr nDtRraL PR IT AL7MaNISTRAT1i3N I14
0 1-2 8
Ct7Y1t.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2591
RTC -762
Responses to Comments
TRMSIT NOIRE AND VIBRATION It'1PACT ASSJ3SKENT 3'ANUAL
equipment vary greatly on factors such as the type of equipment, the equipment model, the operatirn being performer, and the c=Ntdl ,or of the equipment. Typi€ally, the dominant source of noise from most construction equipment is the engine, often a diesel engine, which usually does not have sufficient muffling, In other rues. such as impact pile -driving or pavement -breaking. noise generated by the process dcarnnvatei:. Construct p n it can be considered to operate in the following two modes for Construction Noise Assessments:
Stationary — Statilorsary equipment operates in one location for one or more days at a time, with either a fixed power operation (puatrps, generators, conpre sort) Or a variable noise operations (pile drivers, pavement breakers).
Mobile — Mobile equipment moves around the construction site with power applied in cyclic fashion {bulldozers, loaders), or to and from the site (trucks). Movement around the site is corrsidered in the construction noise prediction procedure.
Variation in power imposes additional oompfexity in characterizing the noise source level from mobile equipment. Describe the noise at a reference distance from the equipment operating at full power and adjusting it based on the duty cycle of the activity to determine the Go of the operation.
Typical noise levels from representative equipment are included in Table 7- I.
The levels are based on an EPA Report,fd'l I reasured data from railroad construction equipment taken during the 1976 Northeast Corridor Improvement Project, the FHWA Roadway Construction Noise Model, and other measured data.
For equipment that is not represented in Table 7-I, measure the noise levels according to the standard procedures far measuring the estterica• noise lids for the certification of mobile and stationary construction equipment by the Society of Automotive Engineers-100s�
laDtRAL TRANSIT AOMuNa5TRATIcaI I
01-28
Cont.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2592
RTC -763
Responses to Comments
TRAPtfiIT NOIRE AND VIBRATION It1PACT ASSESSMENT I1ANUAL Table 7-I Construction Equipment. Nolte Emission Levels Equipment
Typical Noise Level SO it
from Source, dSSA
Air Compressor _ 80
Baidwou 8[}
Ballast Equatzer 82
Ballast Tamper 83
Compactor 82
Concrete Mixer 85
Concrete Pump 82
Concrete 'r l brator 76
Crane, Derrick 86
Crane. ihtoble 83
Dozer 85
Generad.oe 82
Grader 85
impact Wrench
e
Jack Hammer
20 Loader
80 Patter
85 Pfiie-driver (Impact)
101
Pie -duvet (sank)
95 Pneumatic Thal
85 Pump
77 PYaiI Saw
$0
Rack brill
95 -7aire'l
85 -law
76 Swirlier
83 Sour
85 Shovel
87 Spike DiriVer
77 Tie Cutter
84 Tie Handler
80 Tie Inserter
85 Truck 8q
3a. Use the metric Lr4;r, to assess construcivn noise- This unit is appropriate becasase L s can he used to describe;
■ Nose level from operation of each piece of equipment separately, and levels cars be combined to represent the raise level from all equipment operating during a ,given period
■ 1�14ise level during an entire phase
■ Average noise over all phases of the construction
3b. Use Eq. 7- I to predct construction nose impact for major transit protects. considering the noise generated by the equipment and noise propagation due to distance, Calculate 414 eq-uap for all equipment individually, then use decibel addition to sum the L.nes,r rr ip for all equipment operating during the same time period, See Appendix 8. I .I for information on decibel addition.
FEDERAL TRANSIT rDNUNtSTRATIC3N I1
01-28
CC nt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2593
RTC -764
Responses to Comments
TftMSIT NOISE AND VTBRATION IA'1PACT ASSE SM'iENT f1ANUAL Lr", L ± 1O to Ad D Eq. 7-f
I IuM - w sir)rr � !r� rr } 4log S©)—10�1og(.a)
wherw
= ��ranat a receiver tram the operation of a single p ece of equipment over a specilfed time period, dfiA
= noise emission slit park rfar piece or quYpment u
the reference distance of SO k dBA
= usage factor tt3 account lot the fraction of tirrIt tai rht equipment is in use over the specified rune period
= distance fromthe receiver to the niece, of equipment. ft = a constant that accounts for topography and ground effects Determine the quantities for Eq, 7-1 based on the level of assessment described below_
• A gexeral a-i-essrrrent of construction noise is warranted for projects in an early assessment stage when the equipment roster and schedule are undefined and only a rough estimate of construction noise levels is pra€tical.
• A detailed analysis of construction noise is warranted when many noise - sensitive sites are adjacent to a construction project or where contractors are faced with stringent loud ordinal -Kim or heightened public concerns expressed in early outreach efforts.
Complete the appropriate assessment for each phase of construction. Major construction projects are accomplished In severrl different phases. Each phase has a specific equipment mix, depending our the work to be accomplished during that phase. Asa result of the equipment miv„ each phase has its own noise characteristics; some phases have Ii gherr continuous noise levels than others, and some have higher impact noise levels than other.
Option A:. Genera) Assessment - Determine the quarrtlties for Eq. 7-I based on the following assumptions fora General Assessment of each phase of construction,
• Noise emission level (Lnttrs zrm) — Determine the emission level at 50 ft according to noise from typical construction equipment described above and Table 7-I.
• Usage factor (Adla+.,j - Assume a usage factor of I. This assuirsus a tame period of one -hour with full power operation. Most construction equlprnerrt Operates continuously for periods of one -hors or more during the construction period.
Therefore, 141og(Adj,..40 = Oland can be omitted from the equation. • Distance (D) - Assume that AI equipment operates at the center of the project. or centerline for guideway or highway construction project $LDERAL TRAII5IT ACrMrNtSTATrf3N I17
01-2s
ccnL-
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2594
RTC -765
Responses to Comments
TRIV4SIT NOIRE AND l§BRATION It'1PACT ASSE SMENT 31ANUAL • Ground effect (G) — G = 0 assuming free -field conditions and igrror rrg ground effects_ If grormd effects are of specific Importance to the assessment, consider using the Detailed Analysis procedure.
Only determine the L ,pt„i for the two noisiest pieces of equipment expected to be used in each phase of construction. Then, sum the levels for each phase of roonstn_tttion using decibel addition.
Option B Detailed Analysis — Determine the quar>tithN for Eq. 7-I based ❑n the following assumptions for a Detailed Analysis of each phase of construction.
Alternatively, for detailed, long -terms, and complex construction projects or projects near a particularly sensitive site the Fl-IWNs Windows -based screening tool, 'Roadway Construction Noise Model (RCNM)," can be used for the prediction of construction nolst,it4i
• Noise emission level (grnrtsJ, — Measure Der certify the noise emission level for each piece of equipment.
• Usage facto (AdJurage) — Long-term construction project noise impact k based on a 3D -day average L. the times of day of construction activity (nighttime noise is penalized by I0 dB in residential areas), and the percentage of time the equipment is used during a period of time that will affect A din; sirar-
For example, an 8 -hour Lrg,r is determined by making Adfoga .wthe percentage of time each individual piece of equipment operates under foil power in that period. Similarly, the 30 -day awe La is determined fmm the t#uf trsrtyr expressed by the percentage of time the equpment is used duringthe daytime hours (7 a.m. to 14 p.m.) and nighttime ( IC p,rn. to 7 a_m_) separately; over a 30 -day period. To account for increased sensitivity to nighttime noise, the nighttime noise levels are as lusted by Ifs d8 in the Lo-, computation (see Appendix B.I.4.5). • Distance (D) - Determine the location of each piece of equipment doing operation and the distance to each receiver.
• Ground effect (G) - Use Table 4-26 in Section 4.S. Step 3 to calculate G to account for the site topography, natural and manmade barriers, and ground effects.
Compute the 8 -hour l+plia ( f'er1r*aie:yialrcrl) and the 30 -day average La„ (£dnerrrair(3Ct4„ yd for all equipment expected to be used in each phase of construction separately_ Then, sum the levels for each phase of construction using Eq_ 4-56 and Eq. 4-57 in Table 4-32.
Step 4: Assess Construction Noise Impact
Compare the predicted noise Weis from the Quantitative Conm-true-don Noise Assessrnew with import criteria to assess itnporct from corrstructian noise for each phase 'If ctlrrstructiarr.
FfD R L Pis, IT AL7MrNt5TRATa(}N I1
01-28
Cont.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2595
RTC -766
Responses to Comments
TRAP T Nfl15£ AND V RATION IA'1PACT ASSE SMENT MANUAL
Na standardized criteria have been developed for assessing construction noise impact. Consequently, criteria must be developed on a pr*ct-specific basis unless focal ordinances apply, As stated earlier in this section. local noise ordinances are typically riot very useful in evaluating construction noise. They usually relate to IniSatnce and hours of allowed activity, and sometimes specify limits in teams of maximum levels, but are generally not practical fat assessing the impact of a corrstniction project. Propect construction noise criteria should account for the existing noise environment, the absolute noise levels during construction activities: the duration of the corixiiruetion, and the adjacent land use- While it is 1 —Dot the purpose of this manual to specify standardized crtena for construction noise attract. the ra laving guidelines can be considered reasonable criteria for assessment, f these erite-ia are ewes .etc red, then may Fri adverse community reaction,
The construction impact guidelines art presented based an the level of quantitative assessment.
Option A: General Assessment — Compare the combined �y_M,uTchry for the two noisiest pieces of equipment for each phase of construction determined in Section 7, I. Step 3 to the criteria below. Then, identify locations whet the level exceeds the criteria.
Taiga 7-Z. General Assessment Construction Noise Criteria Land Use
Lvn.c iiiptirail, dBA
Day Night !
Residential la B
Commercial
100
I GO
Industrial
1 I00
100
Option Eli Detained Analysis —Compere the combined ,Gpgml,g+poi,r•J and the combined L,rn_£;r r snrrr,yl for all equipment for each phase of construction det:errnlned in Section 7.I, Step 3 to the criteria below. Thor_ identify locations where the level exceeds the criteria.
Table 7-3 DelaHed Analysis Construction Noise Criteria
Land Use
LQ+rn,.rarycrkrl, dBA
Day Night
Jror,,rq++ygan..A'ypl, dBA
30 -day Average
Residential
i
7.0 75
Commercial
05 B5 I
Kr
Industrial 9[v • 9,0
I
8S'
se a 24 -lion lga2tkiBresaead of Lh.owr,xr{.,.
Step S: Determine Construction Noise Mitigation
Measures
Evolucrie the need for mitigation and seteccl appropriate mitigation rrtevsurres al:ARN. TRAMIT ADNIANt5TRATs(}N 174
01-2s
ccnt_
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2596
RTC -767
Responses to Comments
TRAPISIT NOIRE AND l§BRATION It'1PACT ASSE SMENT t1ANUAL Where potential Imparts have been identified according to Section 7.I, Step 4, evaluate appropriate cnntrnl measures. Include tir criptions of how each affected location will be treated with one or more mitigation measures in the environmental document
5a. Determine the appropriate approach for construction WISE COMM_ Categories of approaches rriclude
• Desigti considerations and project layout
o Construct txaise barriers, srrch as temporary walls ca- piles of enacavated material, between, noisy activities and noise -sensitive receiven,
• Re-route truck traffic away from residential su, ten- Select streets with the fewest homes if no alternatives are available, o Site equipment oil the construction kit as far away lrorn noise - sensitive sites as passible
• Construct walled enclosures around especially noisy activities or (Iusters of noisy equipment For example. shields can be tts$.t around pavement breakers, and loaded vinyl curtains can hi- I under elevated structures.
• Sequence or operations
▪ Combine noisy operations to occur in the same time period. The total noise level produced will not be substantially eater than: the level produced if the operations were performed separately. o Avoid Fieldale activities. Sensitivity to noise Increases during the nighttime hours in residential nrjghborhoods,
✓ Alternative construction methods
a Avoid impact pile-diivirig where possible in noise -sensitive areas.
Drilled piles or the use of a sanit:lvibratory pile driver or push pile driver are quieter alternatives where the geological wnditions permit their use.
▪ Use specially -quieted equipment, such as quieted and enclosed air compressors and properly -working mufflers on all engines; o Select quieter demolition methods, For e -sample, sawing bridge decks into sections that can be loaded onto trucks rIts in lower cumulative noise levels than impact demolition by pavement breakers.
Include descriptions of hew each impacted Itxation will be treated with one o r more mitigation measures in the environmental impact assessment when possible.
5b. Describe and commit to a mitigation plan that will be developed later when the inkcxmatkm k available to make final dedsians (not often available during the project development phase) on ail specific mitigation measures_ This may Inc the case for lain, complex projects, The objective of the plan should be to minimize construction n noise usingall reasonable (e.g., cost vs. benefit) and feasible (e,g,, possible to construct) means available_ nDERAL tRAN5IT A NI Nr5TRATM 'N
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TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL
Coan.praneruts of a mitigation plan may include Some or all of the following provisions, which should also 'Le specified In construction Contracts • Equipment noise emission limits - Equipment noise limits are absolute noise limitsapplied to generic uses of equipment at :t reference distance (typically SO ft). The limits should be set Ro higher than what is reasonahlyachlevahle for well-rnadntafned equipment with effective mufflers. Lower limits that require source noise control may be appropriate for certain equipment when needed to minimize community noise impact. If r,easortable and feasible. Provisions could also be included to require equIprnent noise certirIc tkon testing prior to use ore -site,
• Lot -line construction noise limits - Lot -line construction noise Ilrrrlts are noise limits t#rat apply et the lot -line of specific noise-senoiltive properties. The limits are typically speclPled in tprrns of both noise expostrre (usually Lojl own a 20 -30 -minute period) and inaxwn s noise level. They should be based on local Raise ordinances if applicable, as well as pre -construction baseline noise Ids (usually 3 to 5 dB above the baseline).
• Operational andlar equipment restrictions - It may be necessary to prohibit or reshrkt certain 40nStru thhn equipment and activities near residential areas during nighttime hours. This Is particularly true for activities that generate tonal, impulsive, or repetitive sounds, such as track -up alarms, hoe ram demolition, and pfle-drl ing
• Noise abatement requirements - fn some +Aces, specifications may be provided tear particular noise control treatments based on the results of the design analysis arideor prior commitments made to the public by civic authorities- An example would be the requirement far a temporary name barrier to shield a particular caanmunity area from noisy construction activities.
■ Noise monitoring plan requirements - Plans can be developed for pre -project rose monitoring to establish baseline noise levels at sensitive locations, 4.5 well as for periodic equipment and lot -line noise monitoring during the cranstouction period, The plan should outline the measurement and reporting methods that will be used to demonstrate cornpliarvice w'th the project Raise limits.
■ Noise control plan requirements - For major corn -traction projects, preparation and submission of noise corttrof plans on a periodk basis (e.g„ eve), sirs months) are generally required. These plans should predict the construction noise at noise -sensitive receiver locations based on the proposed construction egtiprnent and methods., Ili the arralyxis predicts tlut die specified noise limits will to exceeded; the plan should specify the mitigation measures that will be apps led and should demonstrate the erected noise reductions these measures will achieve. The objective of this proactive approach 15 to minim ice the sEDERAI PRAN IT ADN ororitATION I$I
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TRIV4SIT NOIRE AND l§BRATION It'1PACT ASSE SMENT I1ANUAL likelihood of cornmonity no complaints by ensuring that and necessary mitigation meastin are Included in the construction plans_ • Compliance enforcement program - If construction noise is an issue h the community. it is important that a program be implemented to monitor contractor compliance with the noise control specifications and mitigation plan_ k is recommended that this function be performed by a construction management team oo behalf of the public agency, • Public Information and corttpladnt response procedures - Tcs maintain positive community relations, it is recommended to beep the public informed about the construction plans and efforts to minimize noise, and procedures should be established for prompt response and corrective action to noise complaints during construction, Most of these provisions are appropriate for large -stale projects, where construction activity will continue for many months, if not years. The Finked references contain more information on construction noise for major transportation prvjects,! s*i
7.2 Construction Vibration Assessment
Construction activity err result in varying degrees of ground vibration. depending on the equrpmiatt and methods employed_ Operation of construction equipment causes ground vibrations that spread through the ground and diminish in strength with distance. Buildings founded on the soil near the construction site respond to these vibrations with varying results, ranging from no perceptible effects at the Best levels, low rumbling sounds and perceptible vibrations at moderate levels, and slight damage at the highest levels.
While ground vibrations from construction activities do not often reach the levels that can damage structures, fragile buildings must receive special consideration. The constructionvibration criteria include consider Alan of the building condition_
The key elements of the Construction Vibration Assi smerit procedures and recommended workflow are as follows=
Step t Determine level of construction vibration assessment Step 21 Use a qualitative construction vibration assessment Step 3: Use a quantitative construction vibration assessment Step 4: Asses construction vibration impact
Step SSI Determine construction vibration mitigation measures FaDEilA1 TMN IT ADNIIINt5TRATlf}N Ie:
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TRMSIT NOIRE AND WBRATION IA'1PACT ASSE SMENT 11ANUAL
Step I: Determine Level of Construction Vibration
Assessment
Dererrnine iiie appropriate tenet orAseSsnrent based on the scale and type or the prole a and the wage of errvircarmerrtrrl review.
I a. Determine if an assessment is required.
Construction Vibration Assessments are not required far many small protects including.
• Installation; of safety featurrs like grade-crossiing signets • Track improvements within the ROW
• Erecting small buildings and d faciilities, which are similar inscale to the surrounding development
I b. Determine whether a qualitative or quantitative assess men t is requiired-
• Qualitative Construction Vibration Assessment - A qualitative consu reenter vibration assessment k appropriate for protects where prolonged annoyance or damage from constructionvibration is not expected, htrr- exaanple, equipment that generates little or no ground vibration —such as air compressors, light trucks, and hydraulic loaders — only require qualitative descriptions_ See Section 7.2, Step 2 fur more information an qualitative construction vibration assessrnenrs. • Quantitative Cotstrucdon Vibration Assessment — A
quantitatIve construction vibration analysis is appropriate for projects where construction vibration may result in building damage or prolonged annoyance. For example, activities such as blasting, pile - driving, vibratory compaction, demolition, and drilling or excavation near sensitive structures req.uii a quantitative analysis, See Section 7.2, Step 3 for more Infarmatbon on quantitative construction vibration assessments.
If there Is uncertainty in how to determine the appropriate level taf asse€meat, contact the FTA ite$icnal office.
Step 2: Use a Qualitative Construction Vibration
Assessment
Use a cyricIitaiive cnristroctian vibration assessment to es-Pimate vihratidn for appropriate pre per Section 7, 2, Step I b.
Provide qualitative descriptions in the environmental document d the following elements!
• Chration of conduction (both overall and at specific locationsj' • Equipment expected to he used
• Description of how ground -borne vibration vuill be maintained at an acceptable level
F DEEtA1 T IT ,trOtrNNt5TRATIO1 I 193
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TRANSIT NOISE AND lcBRATION It'1PACT ASSE SMENT MANUAL
Note that the criteria in Section 7_-7, Step 4 do not apply to qualitative assessrnerrts.
Step 3: Use a Quantitative Construction Vibration
Assessment
Use rr rjurrntirutive construction v>nrrtion assessment to estimate vibration fo appropriate projects per Section 7,Z Step i b.
For quantitative construction vibration assessments. follow the recommended procedure in this step. Vibration source levels from typical construction equipment and operations are provided below. and procedures on how to estimate coru7tr-uctlon vibration for damage and annoyance are provided in Steps 3a and 3b; respectively_
■ Vibration Source Levels from Construction Equipment - Table 7-4 presents average source levels in terms of velocity for various types or construction equipment measured under a wide variety of construction activllie. The approsdinate rms vibration velocity levels were calculated from the PPV limits using a crest factor of 4, representing a PPV-rms difference of 13 (f3. hate that although the taut, gores one level for each piece of equipment, there es considerable variation in reported ground vibration levels from construction activities. The data in Table 7-4 provide a reasonable estimate for a wide range of soil conditionssmeigiiraition
Table 7-I Vibration Source Levels for Construction Eq 1prnent Equipment
F PV at 2S Approach -nails
ft. inhec tv'rAt7$ift
Pile Drives (Impact)
upP range
1518 112
cypiic.e
0444
I41
File Driver Doric) up r
range
3734
105
typral
0.17 93
Clam shovel drop Ninny wall)
122132
94 Hlydromill (slurry
in sal
0,
di
wall)
in rink
,09T
75 W9brat ry Roller
0;2I
44 Hoe Rain
0.069
TIT
ionic bulldaser
41:t1B9
$7
Caisson dnilliin&.
i
ts.deduntit
0,0M
8fr
Jaddramnres
003S 1
74 Small badldrsrer
4.0Q3
Se
-Rr+FS volecliy In &caw s Y nu I mkrre-n.Psat
3a. Damage Assessment
Assess for building damage for each piece of equipment i tidividually.
Construction vibration is generally assessed in terms of peak particle velocity (PPV), as described in Suction S.I .
,FLDERA1 ift4MIT ,aL7MiNISTRAT*t3N Ii
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Responses to Comments
TRANSIT NOISE AND VIBRATION IMPACT ASSESSMENT 31ANUAL
• Determine the vibrations source bevel (PPV,. ) for each piece of equipment at a reference distance 8f zs ft as dineribed above and In Table 7-4,
• Use Eq. 7-2 to apply the propagation adtustrnent to the source reference level to account for the distance from the equipment to the receiver_ Note that the equation is based an point Sources with normal prapragation conditions_
25 PPVeofp = PPVrey ac{ L] )t.s
whom
PPV,sqetp
PPVr
Eq. 7.2
= the peak panicle velocity of dbe equipmeent
adjusted for distance, 'nisei(
=the sr■arrce refer crate vlbra-riotread at 73 ft.
inhes
= distance from the egsapment to the recelvrr. ft
3b. Annoyance Assessment
Assess for annoyance for each piece of equipment individually. Ground -borne vibration related to htrrnn ant oyat»e is related to rnss velocity levels, expo sled In udg as described in Section 5.1.
Estimate the vibration level (IL,}usingEq. 7-3.
!;l
Lp.dishrnee = Lcr+sf' — 3° loJq( )I
where.
Lrzrutvarre = the MU vdotity level adjusted for distance, Vd8 the source reference vibration level at 2S ft. YdE
( = diurnice from the equipment in the receiver. It
Step 4; Assess Construction Vibration Impact
Eq. 7-3
[ampere the predicted uibrutirxs kre6 from the QuoruitaWe G nstru[tion Vibration Assessment with ittlpact uitefila to assess kepttct from cortstrucrion vibrauioti.
Assess potential damage effects from construction vibration for each piece of equipnnerst IndividiJally_ Nate that equipment operating at the male time could increa,se Abratltan levels s.ulxtantially, but predicting any increase could be difficult. The criteria presented in this section should be used during the environmental impact assessment phase to identify problem locations that must be addreased during the engineering phase..
Cumpane the PPtf and approximate Id, for each piece of equipment determined in Smtion 7.2, Step 3 to the vihradon damage criteria in Table 7-5, which is presented by buildingi'structural category, to assess impact.qcwil The apprax1nratte rms vibration velocity levels were calculated front the PPV limits using a crest factor of 4,
FbD4RAt. TRANSIT AA7MrNIMATrO1I I84
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TRANSIT NOIRE AND V RATION IMPACT PSSE SMENT MANUAL
Table 7-S Conrtructlort Vibration Damage Criteria
Bubdingi Structural Catogo_q
FPV, inleeu:
Approx mato L`
I. Reinforced -concrete, sleet or rino'hee ino praitee ) {I5
[U2
II. Erylineered concrete and masonry (no plater)
4.3 3$
III. Dian-erigine'esed tin libel aid malloflry batEri' 9 Q.2
44 IV. sail llte s rxcrcmtlly susceptible to vibration dimes
4. I
] I7
ay rn daciEeh YdB re I rairra.insec
Compares the Lv determined in SHtLldn 7. . Step 3 to the criteria fox the General Vibration Assessment in Section 6.2 to assess annoyance or interference with vibration -sensitive activities due to construction vibration.
Step 5: Determine Construction Vibration Mitigation
Measures
&duott lire need for mitigation avid stied appropriate mitigation measures where poteneMil hflmon impacts or building damage from constniction vibration have been identified according to Section 7.2, Step 4
Se, Determine the appropriate approach for construction vibration mitigation considering equipment location and processes,
• Design considerations arid project layout
• Route heavily -loaded trials away from resectentri streets. Select stns with the fewest. homes If no alternatives are available_ • operate earth -moving equipment on the construction lot as far away from vibration -sensitive sites as passihl€:.
• Sequence of operations
4 Phase demolition. earth -moving, and ground -impacting operations so as not to occur in the same time period. Unlike anise the total vibration level produced could be substantially less when each vibration source operates separately.
▪ Avoid ilghturrre activities. Sensitivity to vibration Increases during the nighttime howls in residential neighbra hoods,
• Alternative construction methods
• Carefully consider the use of impact pile -driving versus drilled piles or the use of a sonrcivtbrrtory pile driver of push pile drive- where those processes might create lower vibration le'rels if geological cr;Iattbtinns permit their use.
- Pile -driving is one el the greatest sources of vittrqt.iOn associated with equipment used during construction of a project. The scarce levels In Table 7-4 indicate that sonic pure drivers rrwy provide substantial reduction of vibration levels compared to impact pile drivers- But, there are some additional vibration effects of sonic pile &livers that rrray limit their use in sensltivne locations.
- A sonic pile driver operates by continuously shaking the pile at a fixed frequency, literally vibrating it into the ground- Continuous operation at a fixed frequency may, however, be rriore
:FEDERAL. TRANVI ADNIiNI5TRATICn1 l
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TRIV4SIT NOIRE AND l§BRATION IA'1PACT ASSE SMENT I1ANUAL noticeable to nearby residents, eVern at lower vibration levels.
Furthermore, the steady-state excitatnon of the ground may induce a growth in the resonant response of building
components. Resonant response may be unacceptable in cases of fragile buildings or vibration -sensitive manufacturing processes_ impact pile drivers, however, produce a high vibration level fora short tine {O.2 seconds) with strfiklent time between impacts to allow any resonant response to decay. - Select demolition methods involving little to no impact, where possible. For ecarrnpie, sawing bridge decks Into sections that care be loaded onto rrutks resultss in lower tnibra ti i levefs than impact demolition by pavement breakers. Milling gerielates lower vibration levels than excavation using clam shell or chisel drops.
- Avoid vibratory rollers and packers twat. sensttivee at.ea;_ 5b. Describe and commit to a mitigation plan that will be developed and implemented dludng the engineering and construction phase when the information available during the project development phase will not be surf icient to define specific construction vtbratl°n mitigation measur�_ The °Elective of the plan should be to minimize corrstruction vibration damage using all reasonable and feasible means available, The plain should include the following components:
■ A procedure for esrablishing threshold and limiting vibration valie for potentially affected structures, based on an assessment of each structure's ability to withstand the loads and displacements due to constrwciIon vibrations
• A commitment to develop a vibration monitoring plan during the engineering phase and to Implement a compliance monitoring program during construction
F DERA1 TII,AN'3IT ADMrNt5TRAT* N Ice
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TRMSIT NOIRE AND l§BRATION It'1PACT ASSESSMENT f1ANUAL
SECTION Documentation of Noise and
8 Vibration Assessment
The level of required documentation is determined according to the project class of action. Section 2. I covers the appropriate class of action (EIS, EA or CE} for different projects. If there is uncertainty in the appropriate level of documentation, contact the FTA Regional office.
The noise and vibration analysis must be articulated to the public Ina clear, comprehensive manner for all levels of documentation, The technical data and information necessary to withstandscrutiny in the environmental review pnacess must be documented in a way that remains I ntelligible to the public_ Justification for all assumptions used in the analysis, such as selection of representative measurement sites and all baseline conditions. must be presented for review.
A separate technical report or memorandum is often prepared as a supplement to the environmental document A technical report is appropriate in cases when including the data from the assessment would create an unreasonably long environmental document. The details of the analysis are important for establishing the basis for the assessment. Therefore; all details in the technical report should be contained in a well -organized format for easy access to the information.
For large-scale projects. the environmental document should contain a summary of the essential analysis information to provide subject matter context and the analysis fmdings. Far these projects, separate technical reports are usually prepared as supplements to the EIS or EA and referred to in the environmental document. For smaller projects, or projects with minimal noise or vibration impact, all of the technical information may be presented 6n the environmental document itself or Ina technical memorandum. Other projects might have no potential for nose or vibration Impacts. For those projects, that environmental documentation should explain that rho noise or vibration impacts are eaapeccted.
This section provides guidance on presenting the necessary noise and vibration information In the environmental document (Section 8. I ) and the associated tedhnical report (Section 8.2)_
al Environmental Document
In the environmental document provide asummary of the comprehensive noise and vibration information Irons the technical report and emphasize the salient points of the analysis in a format and style that the public can understand_ Smaller pr eCts may have alI of the technical information contained within the environmental document so take special care in summarizing the technical details to convey the information adequately.
F DIaRAL TRAN IT ADMiNI ATKIN I
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TRANSIT NOISE AhJD lrBRATiON IMPACT ASSESSMENT MANUAL
Step k Choose the information to Include
Choose the apprnprime mile and vibration analysis information to in kite biased on the level of enreenm€ntef review and sire ossacieted documentation Ia. Provide full disclosure (incise and vibration Impacts in the environmental docernent. including identification allocations wIsere impacts +einncst be mitigated below the severe impact level. In general. an EIS describes significant impact and plans to mitigate the impacts. Four EAs, completion of the environmental review with a finding of no significant impact (FONSI) may depend on mitigation being considered for incorporation in the proposed project. The way mitigation is presented in the environmental document depends on the type of impact (noise or vibration) and the stage of project development and environmental review, Projects that meet the retterla of a GE may also regulie the completion al a noise andder vibration analysis, and the results of such an analysis should be documented in a noise memo or the CE d+ocu nentation-
I b. Document noise impacts — Typically, airborne noise impacts can be accurately predicted during the environmental review. For projects that focus en a single alternative, noise impacts ca,n be arurately identified in the draft environmentai document, if mitigation ii anticipated, then mitigation cpticns should be explored in the EA Of draft EIS: firm decisions ien mitigation can be deferred to the Leal document Burt for all protects. decisions on noise mitigation should be made before the final document is approved.
I c. Document vibration Impacts — Predicting vibration Impactsaccurately ins more complex because ground -borne vibration may be strongly influenced by subsurface conditions. The geotechni€af studies that reveal these conchtiorrs are normally undertaken during the engineering use, after the environmental review process is complete. Therefore, the final environmental document will usually riot be able to state with certainty whether mitigation Is needed for ground -borne vi bratioe and noise.
If the engineering phase is conducted at the same rime as the final envirenreental document, report the results of the Detailed Vlbtatten Analysis rn the final environmental document If the engmeerieg phase is conducted after the final environmental document mart the results of the General Vibration Assessment in the final environmental document. 1{ impact is determined, include a commitment to the fine! document to conduct a Metalled Vibration Analysis during the engineering phase to complete the impact assessn7ene Aso. include a discussion on various control measures that could be used and the Iifeelihorrrl that the criteria could be met through the use of one. or more of the measures. It may be possible to state a commitment in the final envrrorrnere l document to adhere to the impact criteria for the Detailed Vibration Analysis, while deferring the motion a! specific vibration control measures until the completion of detailed studies in the engineering phase. 'Mier +workis pond acted after FTA signs its final decision document (i.e.. ROO. combined FEIS/ROD, or FDNSJ), additional documentation, such as a reevaluation of the previous decisions, may be ewes -say. FTA recommends contacting the FTA Regional office directly in these situations.
:FLDERA1 rf+,ANaIT A.DMiNtsTRATrr3N Iai
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Ritz -Carlton Rancho Mirage MND 11942
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TRIV4SIT NOISE AND lcBRATION It1PACT ASSESSMENT I1ANUAL I d. Dmcrlhh mibigati srt measures in the decision document - After the decision document is approved. incorporate the mitigation measures by reference in the actual grant agreements signed by FTA and the project sponsor.
The mitigation measures then become contactual conditions that must be adhered to by the project 5ponsor.
It is typically appropriate to include the following noise and vibration information in the environmental document as described in Section 8-I:
■ The existing canditians (affected environment)
■ The direct impacts Irani operation (environmental consequences) • The construction impacts (environmental consequences) Step 2: Organize information in the Environmentztli
Document
Include informntkan In the jodow.irrg sections of the environmental document separating oin the noise rind Vibration information.
2a. Existing Conditions (Affected Enriranment) - Describe the existing condition (€onditions without the projec ) in terms of the existing noise and vibration cond tlora in this section of the document- Thu primary furicdon of this section} is to establish the focaas and baseline conditions for the discussion of ernvironmental impacts. lndude the following basic information and separate the noise and vibration sections. • Description of nofselvibration metrics, effect' and typical levels Include a targeted summary of relevant Information fi roan Section 3 of this manual. This will serve as background for the discussions of noiselvibratian ieveks and characteristics that will follow in later sections. Provide illustrative material to convey typical levels to the public.
• Inventory of n eivibratitari-sensitive sites — Describe the approach for identifying noise- arid vibratiOri-TainSievC sites as well as the identified sites and sate descriptions. Use sufficient detail to demonstrate completer as. Document these reatIts on a map.
• NoisehilbrUvn measurements — Document the basis for selecting measurement sites, including tables of sites coordinated with maps showing locations of sites. Summarize the measurement approach :and include the justification for the measurement procedures used Present •measurement data in well -organized tables and (Turin with a summary and interpretat,on Cl measures! dar_a. Measurements are often included in the table ot measurement sites described in the previous paragraph. In some cases, measurements may be supplemented or replaced by collected data relevant tea the noise and vibration characteristics of then area. For example. soil Information for estimating ground -borne vibrate pi opagation characteristics may be available from other projects Ln the area.
$ DERAL TMN IT ADMtNtSTRATtt'N I9a
01--E
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Ritz -Carlton Rancho Mirage MND 11942
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2607
RTC -778
Responses to Comments
TRAPIFi1T NOIRE AND ltt&RATION It'1PACT ASSE SMENT t1ANUAL A summary and interpretation of how the collected data define the protect setting is fundamental to this section.
2b, Direct Impacts - Include the following in the discussion on direct impacts due to prngett operatrorc
• Overview of approach - Provide a targeted summary of relent -it information on the assessment, procedure for determining noisefuibratIon imparts as a frarnevrorls. For the Following sections. • Estimated noise/vibration levels - Provide a general description of prediction models u5e3d to estimate project noise/vibration levels.
Describe any distingishing features unique to the project, such as same levels associated with various technologies.
Describe the results of the predictions in general terms first, followed by a detailed accounting of predicted noise levels. Supplement this information with tables and illustrate by contours, cross -sections, or shaded mapping, If contours are Included Ina technical report, it k not necessary to repeat them in tfis section.
• Criteria ribs nnlse'vibratfon impact — Describe the impact criteria for the project In detail aid refenerrce the appropriate section In this manual. Include tables listing the criteria levels or the figures included in this manual.
■ Noiseivibrablian Impact assessment — Present the impact assessment in its own section or combined with the section above Describe the locations, as identified in the screening procedure. where noise/vibration impact is erected to occur without inrplerrieritation of mitigation measures, based on the screening results, predicted'' future levels, testing levels, and application of the impact criteria.
Irrc1ude inventory tables of impacted noise- and vibration -sensitive sites to quantify the Impacts for all nolsehibration-sensitive situ included in the Affected Environment (Existing Conditions) as described in the Existing Conditions section above
■ Noiselvlbratiian mitigation t»erar — Perhaps the greatest difference between the technical report and the environmental document is with mitigation, The technical report discusses mitigation options and recommendations, while the environmental document provides the vehicle for reaching decisions on appropriate mitigation measure.
Begin this section with a summary of the noise/vibration mitigation measures considered for the impacted locations. Describe the specific measures selected for implementation In detail. Also, include any nriERAL reAN31T ADMrNt5TRATw3N 141
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TRMSIT NOIRE AND l§BRATION It'1PACT ASSESSMENT r1ANUAL
appkable, pe fflt noise or vitiation polach the project sponsor may have in plane_
In cases where it is not possible to commit to a specific mitigation measure in the final environrn ental document, it may be possible to commit to a certain noise/Abration le, l- for example, the environmentel. document could'mktde a commitment to meetor• exceed the impact criteria specified in Sections 4.1 and 61, • unavoidable adverse environmental effects - if It is projected that adverse noise/vibration impacts will resuhr after all reasonable abatement measures [ewe been Incorporated, Identify theet impacts hi this sfxtion,
lc. Construction Impacts - Dlstriss oonstructroe Impacts in the environmental document's, sect] nn on construction Impacts: if present If. because of the scale of the project the envIroneneread document does not have a separate coretnecti0n impacts section, then the construction impacts should be disused with the rest of the resetarce impacts.
When a special section on construction nolselvibration Impacts is included in the document. t should be organized according to the comprehensive euchre en king -tern impacts described above. For reelects with relatively minor affects, include, a brief summary of Impact_
8.2 Technical Report on Noise and Vibration
The techeicaal restart is Intended to present cemplete technical data and deser'peon & in a manner that can be understood by the general public,but is more technical nical than the inlormation found In the environmental docuttierit. x411 necessary background information should be present in the technical report, inchudirlg tables, maps. charts, drawings, and references that may be too detailed for the envlronreental document but whlch are important In helping to draw conclusions about the project's noise and vibration impacts and reitIgatiorr options.
Include the kellewlrttg major subject headings and key information described raw. If both horse and vibration have been assessed, betide separate sections far noise and vibration with subsections for key information as described below.
Additional details on documentation requirements for the technical report of non-standard procedures and miethotkilVes are included In Appendix G. • Overview - Include a brief description of the project and an overview of the noiselvibratioo concerns to highlight initial considerations in framing the scope vF the study.
• Inventory of NCilselYibt tion-Sensltive Sites - fi%cribe the approach for Identifying noise- and vibration -sensitive sites as well as the identified sites arid site descriptions. Use sufficient detail to demonstrate completenese. Document results can a map.
Peewee PRAN IT ADereire eeTrpN It2
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Ritz -Carlton Rancho Mirage MND 11942
November 2024
2609
RTC -780
Responses to Comments
TRANSIT NOISE AND VTBRATION IMPACT ASSE SPLENT MANUAL
■ Measurements of Existing MaiselVibr ation Conditions
• Document the basis for selecting measurement sites, including tables of sites coordinated with maps shDwing locations of site.
Summarize the measurement approach with justification for the measurement procedures used_
• If the measurement data are used to estimate edsting conditions at other locations, include the rationale and the method of estimation.
Dena- be measur rne4tt procedure'; In detail,,
a Include tables of measurement instruments documenting manufacturer, type, serial number, and date of most recent calibration by authorized testing laboratory,. Document measurement surement periods, including the time of day and lertgth of time at each site to demonstrate adequate repr-esentauon of arrx:ia nt conditions_
▪ Present measurement data in well-orlartized tables and figures with a summary and interpretation of measured data-
■ Additional Measurements Related to the Project— Include detailed description of measurements and results for protects that require specialized measurements at noise- and vibration -sensitive sites, Exarrrples include:
o Outdoor -to -indoor noise level reduction of homes
• Transmission of vibration into concert halls and recording studios a Special source -lewd characterization
■ Predictions of NoiseNihr .tion from the Project
• DecaIhe the lredic-null model used to estimate fut.e project conditions and specific data used as input to the models. Reference the appropriate section in this manual- D current any change or extension to the modus recommended in this manual, so that the validity of the adjustments can he confirmed. See Appendix G for more information.
a Describe in detail the modeled scenarios and why the scenarios were chosen.
a Taholate camrputed levels and illustrate: by contours, cross setituans, or shaded mapping. Illustrate noise/vita anon Impacts with base maps at a stile with enough detail to provide reference for the beation. ■ NoheNibratiatr CrIteria
a Derribe'the impact criteria for the profit In detail and reference the appropriate section In this manual, Include tables specifying the criteria levels or the figures Included in this manual. • If construction noise ar[dfor vibration assessments were conducted, Include the construction criteria in a separate section with the construction assessment details. See below for more information, rEDERAITRANSITADN NeT1ATrf3N Ivr.
01-28
Ccnt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2610
RTC -781
Responses to Comments
TRMSIT NOISE AND VTBRATION It'1PACT ASSE SMENT I1ANUAL
• Noisellli bration'Impart Assessment
• D crtbe the impact assessment according to the appropriate noise and orr vibration impact assessment se€tions in this rnarual. • I f an alternatives analysis was conducted, present a resulting impact inventory for each ahternative mode or alignment in a format that allows comparison among alternatives.
• Tehulate the inventory according to the different types of affected noise- and vibration -sensitive situ. Present the results of the assessment both before and after mitigation.
• Noise/Vibration Mitigation
• Begin this section with a summary of all treatments considered, including those not carried to final consideration-
• Consider final canddate mitigation treatments separately and provide a description of the features of the treatment, Including costs, emoted benefit in reducing impacts, locations where the benefit would be realized, and a discussion of the practicality of alternative treatments.
▪ Inciude enough noise and vibration impact information to allow the protect sponsor and FTA to reach decisions on mitigation prior to Issusare of act ewir•oo nientaf decision document
■ Construction NoiseiVlbraton Impacts
• Desei•I be criteria adapted for construction noise or vibration if construction noise andfor vibration assessments were €onducted,. • Describe the method used for predicting construction noise or vibration and include inputs to the models such as equipment roster by construction phase, equipment source levels, assumed usage factors, and other assxrred site characteristics.
▪ Present predicted levels for noise- and vibration -sensitive sites and identify shark -term impacts.
▪ In cases where canstructiaat impacts are identified, discuss feasible abatement methods using es - laugh detail to allow construction contract documents to include mitigation treasures,
■ References — Provide references for all criteria approaches. and data • sed in the analyses, as wall as other reports related Lo rile project that may be relied on for information, e.g_, geatechnical reports.
F D RAL TI AMIT ADNIANt5TRATtOPI Ive
01-28
Cc nt.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2611
RTC -782
Responses to Comments
TI APISIT NOIRE AND lcBRATION IMPACT ASSE SMENT f1ANUAL Appendix A: Glossary of Terms
Terminology used through the manual is defined in this appendb044f'i A scan arti deed filter used ID alter the sensitivity of a sound level meter wItlri ect A -weighting to frequency so that the Instrument is leas sensitive at low and high (Ferment:
where the human ear is teas sensitive_ Abbreviated. as dBA Absolute Noise Noise that Interkres with activities Independent of existing nurse levels and is Impact expressed as a faxed level threshold
Accelerometer A
transducer that convertvibratory s vibrato motion to an electrical signal proportional to the ambler -4110n of that motion.
Atn ittt
The pre -project background noise or vlbratlen levet which is often cased Interdta ngeaI l with "mcisting noise" in this mutual.
Amplitude
Difference between the extremes of an oscillating signal Alignment
The horaoutal location of a railroad or transit system as described by curved and isingent track
At -grade
Tracks on the ground -surface.
Automated Guideway
Transit (AG Ti
Guided steed -wheel or rubber -tired transit passenger vehicles operating singly or in stolid -car trains with a fully atatomared system an liked-guiefewsys along au exclusive ROW. AGT includes personal rapid transit group rapid transit and automated people mover -s
Artxiliaries
The term applied to a number of separately driven nraehinei, operated by power from the nobs mere or electric generation. They include the air compressor. radiator but traodon motor blower, and air conditioningevltreptraarit ballast mat A
2- to 3-InclethIck elazwmer mat placed under the nrwmral muck ballast an top of ■ tlglti'slab or packed sub fade.
Ballast Graiwfar
material plated on the waddled for the purpose of handing the track in line and at %prfatu
Res Rapid Transit
R�
A type of busted -stop ban operation that rates on technology to help speed up the Set4ir2 Buses can. operate on exclusive transitwnys., high-occupaiecy-vehleie lanes, expressways. or or dinarl streets.
Catenary
On electric railroad and I,RT systems. the term describing the overhead conductor that k contacted by thermograph or trolley, and ire- twppea t itrWeture Commuter rail
Conventional pusenger railroad serving areas seirrnantriing an urban crony, I'Iost commuter rairoads utir¢e Iocomotnre-hatted coaches. then in push-pull cwnkguratton,
Consist
The total number and type of cars. Itaoorttotives, or transit rehules Ina trainer.
Continuotie welded
rail
A number ol rails welded together to farm unbroken lengths al (rack without gape or pints.
Corrupted wall
A rough canditiaar of alternating ridges and grooves which develops on the rail head In service.
Crest factor The rata of peak particle velocity to maximaum ISMS atupitude in an 'melee signal.
CriterFa plural farm of "criterion,' the relationship between a measure of exposms Oita. round or vttratsot Ievd) and Its corresptandltrg effect The transverse member of the track structure to which the rails are spiked or Gross de otherwise fastened to provide proper gage and to cushion distribute. and transmit the stresses of traffic tIrougla the ballast to the tracking Crossover Twc tunirruts with the track between she loopairlifted to loran oomfnuo+es passage between two nearby and generally parallel tracks_ Cun7daRlve The summation ol individual wounds into a shale total value related to the effect over time -
Cut A terrain feature typically created to allow for a trackbed to be at a lower I than the sill ruunding g c uut t
FEDERAL TRANT,IT a rt)MaNaSrRATrpN Iv'S
01-28
Cant_
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2612
RTC -783
Responses to Comments
TftAPSIT NOISE AND lcBRATION II'1PACT ASSE SMENT MANUAL [
lee Decibel.
Se A-weigltung.
Oedbe7
The standard unit of measurement for sound pre -care level and vibration level.
Technically. a detdbel is the unit al level which denotes the ratio between two quantities that are proportional to power. the number of ciccibels is IO times the logarithm of this ratio. Alr1resrated as da.
DMU
f]ieseJrpowered multiple udr See Multiple Unit_
DNL
See L.,..
®actri6cation
A term used tea describe the lint -illation of over head wire tar shit -d rdill pwr p er distribution facilities to- enure operation of trains.
Embankment
A" bank of earth, rock or other material constructed above the natural ground lerreM
Equivalent lend
The level of a steady sound. which. in a stated titan period and at a stated local!on, has the saute sound energy as the time-varytirtg sound. Also. written as E.g, Everit
A pm.ssbyof a vehicle (e.g, train, bus, or car) of any slag consist' Ferry
A transit mode comprised of vessels to carry passengers andi'or vehicles over a body of caster.
Fixed devray
A pubic transportation facility with a separate RCM" for the exclusive use. al public transportation and other high -occupancy vehicles,
Range
The wer[iuI proicalon along dse Inner iiru of a wheel that serves, together with the - corresponding projection of the mating wheel of a wheel set. to keep the wheal set on the track
floating slab
A apedel track support system for vibration Isola -nom conadssmg of o'aiucrecs sla[#x supported on resilient element,, usually rubber or similar elastomer_ Force density
Force density is the forte per i 8ot diiscarx'e along the track in 1Iv'ftr'. The torte density level is the level In d=ecibels of dm form density relative to I Ib!lt" and describes the vehicle force that excites the sollirock surrounding the transit etrturtum.
Frequency
The number oil times that a periodically occurring quantity repeats irtell in a specified peno l y/'lith reference to noise and vibration signals. the °Umbel Id cycles per second.
Frequency spectrum
Di giblet -ion of lreguency tamponents of a noise or vibration signal.
Frog
A trade structure used a.t the intersection of two running rails to provide support for wheels amid p retagrwfays tor then- lenges, thus permitting wheels on either rail to cross the other_
Gage {of track)
The distance between the rails on a track.
Grade crossing
Time point where a rail line and a motor vehicle road intersect at the same vertical elevation,
Guideway
Supporting sructira to forma rack for mulling or magnetimilly -hriebitad veihidesa, Head -End Power
EF)
A system of furnisleng electric power fora complete rail`rray train from a single generating plait Intl?? Itscoinodve.
Heavy rail
.
See Pal Rapid transit
Hertz (Ht)
The unit 8f acoustic or vibration frequency represeslydnb cycles per second.
Hourly average sound
level
The tirrmnveraged Aawelgbde'd sound lam', owl- a I -hour period, usually calculated between inte rsl hours. Abbreviated as L, .. .
HybridBus diesel
A rubber-tifetii chi that�eatures a hybrid de T -electric propulsion system_ A engine runs an electric generatoi that powers the entire vehicle induding elearfc drive motors that delver Rowel to the wheels.
idle
The speed at which an engine runswhen it is not under load_ Intarmedia[e Captivity A
Transit OCT) than
u.insit system with less capacity than rail rapid transit (RRTj, bit ntore:capaclty typcal bus operations. Examples of CT include bus rapid transit {SRT), automated guideway transit (AGT), monorails, and trolley.
Intermada1 facility
uIKVC-in cal two or MQra lerteei t of craneptetat ern where trarssfers Holy rscrur.
Jointed
A system of'oink%ralb with steel members designed to unite the abutting ends of oonaguous cols.
aLDERAL TRANSIT isDN tN[STATION I%
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Cont.
Ritz -Carlton Rancho Mirage MND 11942
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2613
RTC -784
Responses to Comments
TRAPIfiIT NOISE AND VTBRATION IMPACT ASSESSMENT f1ANUAL 4ie
Saar Hourly Average Sound Level.
L4
lacy -Night Sound Lewd. The sowed exposure level lot a 24 -hour day ealrulated by adding the sound exposure level obtained during the daytime (7 a,rn_ to I O p.m_) to I times the sound exposure level obtained during the nighttime (I0 p.m. to 7,am,):
This unit k used throughout the United States far enstironnaental impact assessment Alsa written as DNL
Levi
Equivalent Sound Level. The metric hr cumulative noise exposure over a specific time Interval Is the equivalent sound level
lUghtR Rag Transit
A mode orptrbllr transit with Iran lied velerle^a rn multiple unit, prating in waxed. traffic canditiwts on streets as reel as sections c exclusive POW. Vehicles are generally powered by electrlkrr y from overhead lino
Locomotive
A seLpncrpelied, non c revenue al vehicle designed to convert eleerairutl or mechanical energy Into tractive effort to haul railway cars. See also Power Unlit Main line
The principal line or in of a railway,
Hazier
Magnetically -levitated uehir1e• a vehicle or tr-ai n of vehicles with guidance and propuhien provided by magnrltk forces, Support can be provided by tither- an electrodynamic system wherein a moving vehicle is lilted by magnetic forces induced In the guideway or an eleseromagnetic system wherein the magnetic liking forces are actively energized In the guideway.
Mlidmian sound
The highest exponential -time average sound level, in decibels_ that occurs during a stated time period Abbreviated as Lee. The etandardctad time periods are I second for L.,.... slow, and Oi I25 second for L.., fast.
Metric Measurement
value ora quantitative descriptor used to identify a speckle tneasur cif sound level.
Monorail
Guided transit vehides operating ern or suspended front a single rah, beam, or tube.
Meltimadaf f'npfetx
in this manual, the term mul lmedal project is used to describe a proiece that Includes changes to both transit and highway components in segments of the project Muluple Unit (11U)
A farm referring to the practice of coupling two or more addled -powered or sle€trlc- powered passenger cars together with provision for controlling die o•aeuan r0L{7rS on all units from a single controller
Norse
Any disagreeable or undesired sound or oil —audible distrirballce, Octave hand
A standarcfized division of a frequency spectrum in which the interval tureen two ti'4ttine% is a frequency Fader of 2.
One-third octave A
band
standarditad dmasi[sn of a. hcgtrency Spectrum in which the oeteve bends ire divided into thirds for more detailed information. The interval between center frequencies ix a satin cf I-7-5.
Pantograph
A device for collecting currant from an overhead conductor (crtenary), consenting of a jointed frame held up by springs or compressed air and having a current colector at the toe.
Park -and -ride facility
A parking garage ar dl'or lot used for parking passengers automobiles while they the transit agency la€Iiued and vehicles.
Peak factor
See Crestfaccar.
P m —and -profile
IMappitug used Ire- tr anaporcauon planners 0111 5110M Ibroatalasiwnxl ilia videos (x- and y axes) on the same page as two-dimensional profiles On and z=amen) of a road or u.ack
Peak Particle Velocity
4PPV)
The peak signal value of eat os illakit vihrauort we eiky. waveform. Usually expressed in in€he+se€ond in the United States.
Peak -¢u -Peak (P -P')
Vallee
Of an oscillating quantity, the algebraic difference between the extreme values of the quantity,
Power unit
A self-propelled vehicle, running on rails and having one or more electric a,rWrorrs that drive the wheals and thereby propel the locomotive and train. The motors obtain electrical energy either from a rail laid near, but insulated from, the track rails. or from a wire suspended above the track_ Conoct with the overhead wire is made by a pantograph mounted on tear of the unit
Project segttrerrt
Portions of a proje€t witli similar characteristics,
q17iRAL TRAMIT ADMINISTRATION 197
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RTC -785
Responses to Comments
TRMSIT NOIRE AND V RAT)ON IMPACT ASSESSMENT f1ANUAL
Pure thane
Sound or a single frequency.
Regius of curvature
A measure of the severity of a Curve in a tt ack VI aacture based asn the lerigdr of the radius of a chile- that would be Itirmed ill the curve were nantinued.
Rail
A rolled steel shape, commonly a 7 -section. designed to be hid end to end in two parallel lines on cross ties or other siemble supports to form .a track far railway rolling mode.
Reif Rapid Transit Often
(1tRT)
called "Heavy Rail Transit" A mode oI public- transit with Cracked vehicles in multiple sings operating hi exclusive rights -of -tray. Trains are generally powered by electricity from a third rail' alorigndk the tra:k-
Reiet.10
A stationary In-fleidposition at which noise or vibration levels are speediest Relso tar Hp's,' Impact
_ Ndse Increase above existing levels.
Resonance frequency
phenomenon chat oeerira in a strr«t-wre under Cttlittl datn of forced edbrarJon arrch that any grange In Irequency of excitation results in a decrease In response Iyght-of-4Vay
Abbreviated as ROW. Lands or rirthts used or held for railroad or transit alteration_ Root F1ean Square
(ems)
The square root of the mean -square value of an oscillating wxvMorm, where the rnearasquare value is obtained by squaring the value of amplitudes at each instant of dme and then averaging these values over the sample time RIIS Velocity Lewd
See Vibration %/clarity Leval
SEL
See Sound Exposure Level.
Sound Exposure Lsvcl
The level of sound accumulated over a given time int+errral or event Techrdicaily, the sound exposure level is the level of the time -integrated mean square A -weighted sound for a stated time interval or event, with a reterehce time of one second.
Abbreviated as SEL
Sound
A physical disturbance in a medium that is impable of being detected by the human. ear,
Spectru m
See Frequency Spectrum
Sub -ballast
Any material of a superior' character. which is spread on tvia threshed svbgrade of the roadbed and below the top -ballast, to provide better -drainage prevent upheaval by last, and better distribute the load over the 'roadbed- tlbglrade
The finished turbos oldie roadbed below the ballast and track.
Suburban A
btlt,
bus similar to an Intercity bus with Ngh•barksd seats but no luggage c ompartmbus often used in dress mode to city ratters from suburban locations.
Switch
A trade structure used to drvert rolling stock from one track to another.
Ta5r ent track
yuck withoutctunature
T,1
An assembly' of rail. ties. and lr+stenings. over which cars, for, n^iaal'vr , and trains are ha7 w d,
Traction motor
A specially designed direct current sere --wound motor mounted on the trucks rail' lacamotives and self-prnpahed cars to drive the as:fet
_ .,inset
A group of tousled ears imbuing ng at least one power hint ,ir vdtarer
Device designed to receive an I non, signal of a given kind (motion, presume,. heat etc) and to provide an output signal of a digerent kind (electrical voltage amperage, etc-.) in such a manner that desired c?hatacterlstles of the input signal appear In the output signal for measurement purposes.
Transfer motility
Transfer mobility is the complex velocity response produced by a paint forceas a function of frequency and represents the relationship between a vibration source that excites the ground and the resulting vibration at the ground surface.
Transit center
A fixed location where passengers interchange from one route or vehicle to another, A rulsber-tenet, electrically -powered bus operating on city streets drawing power - from overhead fines..
Trolley bus
Truck
The complete assembly of parts including wheels„ aides, bearings. side frames. bolster, brake ring, wings. and all &noriued connecting components, the function of which is ta_prowde support. mobility_ and guidance to a ralroad car or locomotive Trunk line See
Mainline. The nsainine of a committer railroad where the branch Ella vatic is conhbined-
FhDhRAL TRAMIT ADNIIINt5TRAT O1 I I0�
01-28
Cant.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2615
RTC -786
Responses to Comments
TIW4S T NOIRE AND l§BRATION IA'1PACT ASSESSMENT MANUAL
Turnout
An arraugetner1t of a "whch and a frog with dolor* rails. by means of which rolling irtock may be diverted from one track to another.
VdB
'Sex Vibration Velocity Level_
Vekration Velocity
Level (LV))
Ten times the common logarithm of the ratio of the square of the amplitude of the Rh1S vibration velocity to the square of The amplitude of the reference R?1S vibration tr4ocity. The reference velocity do the United States is one macro -arch per second Abbreviated as Va.
Vibration
An ostillation wherein the quantity Is a parameter that defines the motion of a mechanical system
Wheel Cat
A localized %Kerne on n steel wheel of a rail' veldcic, usually t;auseti byalddsling On steel rails. causing a discontinuity in the wheel radius.
Mee] squeal
The noise produced by wheel rata i nteraceion_ particularly on curves where the radars or+aerraturc.s %mailer than allowed by the separation of the axles 1n a wiled say A1ddelanat relevant aeou5tk rerrrr"mloeV and formulas am dersred to AN$ S1,4-1+19# 4441.
FkDERA1 Ph IT 7L7MNNt5TRATt41.1
01-28
Cant.
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2616
RTC -787
Responses to Comments
TRMSIT NOIRE AND l§BRATION It'1PACT ASSE SMENT I1ANUAL
Appendix B: Fundamentals of Noise
Noise is generally considered to be uriwanted sound. Sound is what we hear when errs ears are exposed to small pressure fluctuations In the air. There are many ways in which pressure fluctuations are geu rated, but typically they are caused by vibrating movementt of a solid object. This manual uses the terms noise and sound interchangeably because there is rto physical difference between them, Noise can be described in terms of three varra'bles: amplitude (loud or soft); frequency (pitchy, and time pattern (oar iability).
B. I Amplitude
The loudness of a sound is described by the sound wave's amplitude of pressure fluctuations above and below atmospheric pressure„ Pressure is measured in Pascals. The mean value of the positive and negative pressure fluctuations is the static atmospheric pressure and is not a useful metric of sound.
However, the effective magnitude of the sound pressure Ina sound wave can be expressed by the ems of the oscillating pressure_ See Figure B- I for an illustration of the rms pressure.
The rms pressure is calculated according to Eq. 0- I. The values of sound pressure are squared and time. averaged to smooth: out variations_ The rens pressure is the square root of this time -averaged valise where
pmts
Pr
i=1
1 prrirv— Ir'V Pe-
t
= sound pr�tsurc
= Indiridull soured pressul e
= number o! samples
index olsumination
Eq. B-1
Figure B -I RMS Pressure Illustration
Most humans with typiml or average hearing can perceive sounds ranging from approximately 7O microPascals to 20 rrtillion microPascals or more. Because of the difficulty in dealing with such an extreme range of numbers, acousticians use a logarithmic scaJe to describe sound levels., Acousticians use a compressed stile based on logarithms of the ratios of the sourwl energy contained in the wave related Lo the square of sound pi— s!ures instead of the sound pressor themselves, resulting in the "sound pressure level" in decibels (dB). The 'B' In dB Is always capitalized because the unit is named after Ale>rander Crahtam Bell, a leading 19th century innovator in communication. $LDERA1 TRAMIT dDNUNIMATp3N 2QQ
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Ca rut.
Ritz -Carlton Rancho Mirage MND 11942
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2617
RTC -788
Responses to Comments
TRAPISIT NOIRE AND l§BRATION IA'1PACT ASSE SMENT I1ANUAL Sound pressure level {Lr) is defined as
where
Lt,
pni
Prof
1NoIJau Farnas).fat
re
P
= 201 4110( )
Es) r18
�Fiv
prrf
soquel pont use level, dB
= RPM issued pressure
= 20 rmieroPasas
Eq. B-2
Inserting the range of sound pressure values mentioned above into Eq. B-2 re5ults to a Spical quietest sound at 20 rroknoPascals at d dB. A typical loudest sound of 20 million rolcroPascals 1s 120 dB.
B. w _ l Decibel Addion
The cvinbination of two or more sound pressure levels at a single 1amition requires decibel addition which is the addition of logarithmic quantities sii sound enel y To add sound energy from multiple, t rurpie solrra e5. add the sound energy as shown Eq- 6-3. lflfrxta( PFS + P2` 4. -..t. Phz
= .l )
Prg J
where
Eq. B.3
= sound pressure level dB
pr pz pm ` individual source Rt1S somsd pressures to add prP� ' 20 nncroPascala
A doubling of identical sound sources results in a 3 inei-eas*, as shown matherrratIcally below.
P2
Li, = larot y3(2-=5)
�7z
= ldlrayrnf )+l01cy4r ig(2)
pfd
= 10 a8teP 5) + 3
rof
To add dec bel levels (Inst sd of sound energy) use the following equation' = 1010j 101°it1°I
i
where
aDERAL TRAMIT ADNIANETRATION 201
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TRANSIT NOIRE AhJD l§BRATION IMPACT ASSESSMENT MANUAL
LP
Lo
LF
L1,
sound pressure level, dB
= nun bei of samples
= index of summation
= individual sound prewure level€ dI§
= sound pressure level, d6
= individuati source sound pressure Ievefs to add
The equation Above can be rewritten ae loilOws:
Lb, = '+1044+-+10T'}
= ind"nridual source sound pressure fevers to add
Dedbel addition can be quickly approximated using Figure B-2 where
Eq. B-4
D ff iice in DeOllbete
Between Tow Levels To Bo Added
01-28
Ci nt.
Figure B•2 Graph for Approximate Ilecikei Addition
taDERAL TRAMIT istiNUNi5TRATIf}N 298
Ritz -Carlton Rancho Mirage MND 11942
November 2024
2619
RTC -790
Responses to Comments
TRN4SIT NOISE AND Vf&RAT1ON It'1PACT ASSESSMENT I1ANUAL Example '8r- I Decibel Addition— Identical Buses
Decibel Addition
What is the combined sound pressure level of two identical buses it the noise from one bus reunited in a sound il-rxssute level of 70 dB?
Sane l efoudt-f1g of nlent+eal sown' saurees rewlts In 3.48 Inez°ease; 1, =7111:
= 73
x*mple B-2 Decibel Addition — Two 5out es
Dedbel Addition
Wfrat is the combined sound pressure level of 64 d6 and 60 d6? Using al_ B.-1:
= 10, log t (I 1.114 + 1 [ry15., 1 M1 1
= 655 di 1
Using Figure 11.2i
The x-axis values represent the difference between the two sound Ievels. 64 and 60 dB. The ditieremce between the so-und le,els n this example fs 4, The prim an the curve Darrespdndng to 4 on the..•stain is I.S. The y-awx ++elves represent the increment that is added to die higher IeveVl. l,a =` b4.-1.5
= 655 EfEf
B, I.2 Frequency
Sound is a fluctuation of air pressure. The number of tames the fluctuation occurs in one second is Called Its frequency. In acoustics, frequency Is quantified in cycles per second, or Hertz {Hz). The hearing for a typical human covers the frequency range from 20 Hz to 20,coq F .
Some sounds, like whistles, are associated with a singe frequency; this type of sound is called a pure tone. However. most often, noise is made up of many frequmxim called a specimen. Analyzing a noise spectrum allows for identification of dominant frequency ranges and can assist In Identifying leonine raue cis_ Often a frequency spectrum Fs divided into standardized it equcrwy bards for arralysls_ Most commonly. the frequency bands for transit analyses are octave bands (where the interval between two divisions is a frequency ratio of 2) and one-third octave bands (where the Interval between center frequencies is a ratio of 1225)..;nI
If the spectrum associated with a transit noise sotrci isdrrnfrwted by many low -frequency components, the noise will have a characteristic Ike the rumble of thunder. this is often associated with noise from a stIrway. Mid -range frequencies are often associated with wheellrell noise, and high frequencies may be associated with wheel squeal due to sharp eui ves tan a [rack, The spectrum in Figure 13-3 illustrates the full rarer of acoustical uercies that can occur near a transit system. In this example, the raise spectrum was measxred near a train on an elevated steeI structure with a sharp curve.
F pERAJ: 'MAMA' namiNl5TRATIGNN 1,93
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Cent.
Ritz -Carlton Rancho Mirage MND 11942
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2620
RTC -791
Responses to Comments
TRMSIT NOIRE AND l§BRATION IA'1PACT ASSESMENT IIANUAL
113 Octave band Sound pressure Level -- Re 2OuPa
120
110
100
99 �4a
70 60
59 31.5 133 125 250 504 1001) 1000 4000 i3000J
g Octave Band of Transid Train on Elevated Str cI ure -- 01-28
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Figure 8.3 Noise Spectrum of Transit Train on Curve and Elevated Structure The human auditory system does not respond equally to all frequencies of sound For sounds normally heard In our environment. low frequencies below 250 Hz and frequencies above l0.000 Hz are generally o nsidr ed less audible than the frequencies In between. This is because our ears are lees sensitive In those areas. To better 'represent human hearing, frequency response functions were developed to characterize the way people respond to different frequencies, These are referred to as FU. B-, and C. weighted curve and represent human auditory response to normal. very loud, and extremely loud sound levels, rie.pectively. Environmental noise Is generally considered to be in the normal sound level rave; and, therelore, the A -weighted sound level is considered best to represent the human response.
The A -weighting curve is shown in Figure f3.41. This curve illustrates that srsi.indis at 50 F -Is would have to be amplified by 30 d$ to be perceived as loud as a sound at 100D Fez at normal sound levels.
FEDERAL TRAMIT AVIAN15TIYATIr3N 201
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TftAPISIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL 2 5 100 2 5 1 O
Frequency (Hz)
2 5 10,0410
Figure B-4 A -Weighting Cure
Law frequencies have longer- wavelengths of sound (cycles are IesS frequent) and, conversely. high fregµencies have shorter wavelengths {cycfm are more frequent). The size of the wavelength in feet a dependent on frequency and speed of sound as follows:
where
f
A
= c
= frequency in cycles per second. Ii
= wavelength, k
= speed of sound. fthec
Eq. B-5
The speed of sound in air varies with temperature; but at standard conditions. It Is approximately IOC* ft per second. Therefore, at standard conditions, a frequency of 1404 Hz has a wavelength of I toot and a frequency of S0 Hz has a wavelength of 20 ft. The scale of these waves explains. in part, the reason humans perceive sounds of IC40 Hz better than these of SO Hz. A wavelength of I foot is similar to the s1ce of a persons head; whereas, a wavelength o€ 14 ft Js similar to dimensions associated with a house, which is why tow -f requarcy sounds (arch as those rrorn an Idling locomotiv€) are sometimes not attenuated by walls and windows of a #come. These sounds transmit indoors with relatively little reduction in sirength.
B.I.3 Time Pattern
The third Important characteristic of noise is its variation in time. Environmental noise is considered to be a aamb inaticn of all outdoor noise sources. When combined. sources saich as distant traffic, wind in trees, and distant industrial or farming activities often create a bow -level background noise In which rro particular individual source is identifiable. Background noise is often relatively constant from moment to moment, but varies slowly over time as natural forces change or as human activity follows its daily cycle.
In addition to this law -level, slowly varying background noise, a succession Of identifiable noisy events of natively brief duration may be added. These events may include single -vehicle passbys, aircraft fiyavers, F DERAL TMN IT AL7MrNgTRAT1CM 2 5
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TRAPISIT NOIRE AND l§BRATION It'1PACT ASSE SMENT t1ANUAL screeching of brakes, and other short. -term everrCS, Which all cause the poise level to substantsaily fiwcer$te'rona moment to moment
It h passible to describe these fluctuating noises in the environment using singe -number metrics to allow for manageable measurements, computations, and impact assessment. The search frir adequate single -number noise metrics has ericornpassed hundreds of attitudinal survey's and laboratory experiments in addition to decades of practical experience with many alternative metrics.
B. I.4 Noise Metrics
The noise metrics referred to iii this manual are desci ibed in the sections below, B.I.4.1 A -weighted Sound Level: The Basic Noise Unit
The basic noise unit for transit rot is the A.weighted sound level and is described In ANSI S I. I- I994 (49), It describes the noise level at the receiver at any moment in time and can be read directly from noise -monitoring equipment when frequency weighting is set to A -weighting, Figure B -S shows eamples of typiimi A -weighted sound levels for bath transit and non -transit souroees, ranging from approximately 30 dBA (very quiet) to 90 elBA {very loud).
The unit dBA denotes the decibel level is A -weighted. The letter '',11\- inchcates that the sound has been filtered to reduce the strength of very low and very high -frequency sounds try emulate the human response to sound levels as described In .Appendix B. 1.1 This allows for events that are out of the range of human hearing such as hIgh-frequency dog whistles and law -frequency seismic disturbances, to be filtered out. On aver. each A weighted seund level increase of I dB corresponds to an approximate doublingaf subjective louthe.ss-
A-weighted sound levels are adopted as the bvsit noise unit foa- transit noise impact assc-sstnents because they!
• Can be measured easily.
' Approximate the human ear's sensitivity to satands of different frequenciesr • Match attitudinal -survey tests of annoyance better than other basic units, • Have been in use since the early I9'3Us. and
■ Are endorsed as the proper basic unit fcrr environmental noise by most agencies concerned with cr?mmunity noise throughout the world,
nDERAL TRAN IT ADMrNETRATp3N 1ts6
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TIWISIT NOIRE AND VIBRATION IA'1PACT ASSE SMENT TIANUAL Traci salt Svurce9
F'iarl Tromso car i:h1 Sawa err, 14rc
Floe Transit Naar
Trvne an MMWrn Cnr'ria.'M.
Ainel Sthrclloe. 541 MIA
Fipl Tgmut Atren,In 60.0
racy fhra Musa
'Fat. Trnnsw an. Shinn —;
All yL 4{r h
dBA Non-Trsnali Salttnve
Outdoor Indoor
Rae% Da
Jack Mwswwurr
Commis' likaor
✓sir Caaordswr
Lawn WON
Laren TINT
Swap Foam in 'uw
Shoo Tee* MAIM
Fgcd WONT
C1nthee Worm.+
Au COhnA nr19r
Aa ar son Ar:t7ilt
Figure S-5 Typical A -weighted 5ound Lerch
B.I.4,2 Maximum Sound Level (L._) During a Single Noise Event As a transit vehicle appresacches, losses by, and then recedes into the dksta xe. the A -weighted sound level rISSS_ rtes a nrraxiirantt. aid these fades into the background noise. The maximum A -wetted sound level reached during this passby Is called the maxlmim sound level, I'm abbreviated here as is Illustrated in Figure B-6 where time is plotted horizontally, and A -weighted sound level Is plotted vertically,
Although L., k commonly used in vehicle -noise spedrI tiorrs,'" it is not used for transit environmental noise impact assessment L does not include the number and duration of transit events. which are important for assessing people's reactions to rtoise It also cannot be normalized to a one -hour or T4 -hour ctrnulative measure of impact, and [herd`ore, is oat cond1 cive to comparison among different transportation modes. For exarnple, cumulative nuke metri,m commonly L ed in highway noise assessments are t. d, -and Li 0, the noise level exceed for I4 percent of the peal.: hour. ^' For Molise compliance Lesis 04 WAIFS lent. sources. Audi At miming 4mrss wehleles [Adel colttr ,Ittd cctndikiphs wall arnooth wheel and rail coodlrxer, LW., Is typically rnexsuied with the sound fecal meter% cane weighting set to "fast" HoweverIN Penal. of [on4114ss or sta[lamarr Caron. s4uYei iL as usually more aFpraprtatre to use the "slow" setting, ;Ashen sat to "slow" SPund level rneterc mere $ame of she vary-trensleet Awc[uatbns. 'wilt's we neeigible when meesslrsg the swer-J noise level FEDERAL TRANSIT AI)NI NISTRATtaN la
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TRIV4SIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT MANUAL 90 r#0
4 70
Lmax = 96
SEL =0Ti6
ft, III \ \
12 I6
Figure B-6 Typkal Transit Vehlale faassbyr
28 Seccrida
B. I.4.3 Sound Exposure Level (SEL): Exposure from a Single Nose Event
Sound exposure level. abbreviated here as SEL. is the cum ulatave noise exposure from a single noise event. normalized to one second (49). SEL contains the same overall sound ever as the ,actual varyirI sound energy during the event. It is the primary metrac far the measurement of transit vehicle noise emissions and an intermediate metric in the measurement and calculation o1 bath L.,.r,.5and Lam. The SEL metric is A. weighted and is expressed in the unit dBA.
This concept. is Illustrated In Figure B-6 and Figure B-7 where the shaded regions are the sound exposure during and event. The example in Figure B.6 is a transit -vehicle passby and Figure B-7 is an example oaf a fixed -transit facility as a transit bus is started, warmed up. and then driven away. For this event, the noise exposure is large due to duration of the event, SEL it an A -weighted cumulative measure that is referenced to one second. Louder events have grater SELs than quieter events. and events ©'longer duration have greater SELs than shorter events. This is generally consistent with community response to noise. Noise events c4 longer dur3lian are considered mare disruptive than events of shorter dirr atiorr with equal maximum A -weighted sound levels.
A -Weighted Sound
90 o
7p
Lrttax ; 82
SEL a 69.6
ANNI,VVN,
12 16 2il 24 26 Seconds
Frture S-7 Typical Fbacdd-Facility Noise Ercnk
F DIaRAJ: t'It,AN'31T ADNONt5TRATIf3N 20P
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TRANSIT NOIRE AND l§BRATION IA'1PACT ASSESSMENT I1ANUAL Conceptually, the sound exposure lei el can be expressed as:
SEL = ] Otag�u�Tht. i sound ener,9Y
during the event
Mathematically_ the sound exposure lei Is computed as followt where
SEL = 10fri.7au( Y(JClrltu)�
sFl = Sound exposure levet, dBA
N = Number of vutptes
= index rpf surnnwrion
= individual A -weighted sound level, dBA
Eq. B-6
The events shown in Figure B -b and Figure B•7 are compared graphically in Figure &B using a logarfthmic vertical scale, The shaded zones in these fgures indicate noise eq sure over time. The actual event shows the noise exposure over the time of the event, and the equivalent SEL ShOWS the total wise exposure norinalraed to one swami Nate that events I and 2 in figure E -B have different. time periods and noise levels throughout the event, but the same resulting SEL.
SEL is used In transit noise analyses bemuse it
I. Accounts for bath the duration anal amplitude of an event, 7_ Allows a ►miform assssrnenL method For bath transit -vehicle passbys and fixed -facility noise events, and
3. Can be used to calculate the one -hour and 24 -hour cumulative metrics far comparison across different transportation modes.
IFLDERAL T1AMIT r7L7MNNt5TIRATIVIA
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TRANSIT NOISE AND VTBRAT1ON IA'IPACT ASSE SMENT 31ANUAL Evan' 'I Loud N0i5•e for
orlon DUPr7rio11
ENO
7i
Zero Energy ?9.
m d a 12 is 20 24 D 4 9 12 I6 2U 24
Event Lower Maximum Level
for Longer Duration
01-28
Cont.
Figure B,8 All Energy Vfew a# Moue Events
B.1.4.4 Equivalent Sound Level (L,,,l,:r�r)
Tune A.'s 1 sea
11me Axis
1 sec
The metric far cumulative noise axlxrsure over a specific time interval is the equivalent sound level 09).
It is a singk decibel value that accounts for total sound energy from all sound levels over a specified time interval for time period). The time period associated with the equivalent sound level metric can vary for different ty of analyses, This metric is abbrrevioted as L.,r where "t"" is the duration of the time period L, i represents a hypati,etlr:al constant world level and contains the same overall sound energy as the actual varying sound energy durng the ume period "1.-. For most transit noise analyses, an A - weighted, hourly equivalent wu d level is used, abbreviated here as Low. L ik, is epressed in the unit. dBA.
Figure B-9 shows examples of typical unmitigated howl,/ L.,.1's both for transit and non -transit sources ranging from 40 (quiet) to 80 dB (laud). Note that these L,R,,,;'s depend upon bath the number al events during the hour as well as each event's duration, which is affected by vehicle speed. For escample; doubling the number of events during the hour will increase the L,,,,M,by 3 decibels, as will doubling the duration of each individual event.
FEDERAL TRANSIT ADNIoNISTRATKCHN i I e,
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TKAPa;SIT NOISE AND RATION IMPACT ASSESSMENT MANUAL
Trrni1t S®Ures r Non-Tnrrlalt Seuree.
Cormnutiar Tres. 150 mph.
0 par Hour will Ft,rn r3' »N
Gerreetaktr T4arra at 5U+MP
6 pea Hato
Roll Permit Trine el 46 ripa7t �t
12 pe. Hour
Reil !reran Tror,i m 20 rnpt,
1J per Irma
Mat 50PI
l
130
r-- 9 -Lana Hpha+ey
-.-- 6 -Lane Hphwo
- a l one Ulan Arterial Rome
,« 7 Lane StiLvrIm0Airtar40 Road
M rp 5011
Figure 8.-9 Typical Hourly L,pisry"s
An example of sound levels over lime fora single noise event Sikh as a train pa -Wing on nearby tracks is Illustrated in the top frame of Figure B-lo,A6 the train approa€hes, passes by, and then recedes into the distance, the A -weighted sound level rises, reaches a maidnnunt and then fades Into the background noise The equivalent sound level is shown 14 1- three different time periods Figure F- la The area under the curve in this top fl mire is the noise chat reaches the receiver (noise exposure) over this five-minute period_ The center frame of the figure shows sound levels over the one -hour period, including the five- minute period from the top frame, The area under the cure reprFeents the noise exposure for one hour, The bottom frame shows sound levels over a full 24 -hour period and Is discussed in Appendix
8.145.
$WEIRAI. TRANSIT ADNANtSTRATro 'N 3I I
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Pap 511 of 548 in Comment Letter 01
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a^Z
iI '7: la li
TRAP T NOIRE AND VF RATION II'1PACT ASSESSMENT 31ANUAL
5Oma
11 —
1 1" Lour
Leq(1 b a 61 MA
eq{5 sec)
ifrehhJ,
a
24 Flours
Ldn = 62 dill
Leq(24 hr) = 57 dBA
�A�uW�VJ�+l17,
L71 min)
Lagl1 hi'F
NwiLitiala
DI BO iM LIM ID'BC I,D la'JS li]L 12143 £urn 2].Br pm
Typical A-wpigmIod Saurid Leval Varulllon Duet a 24 -Hour Pmiod Figure 1}-10 Example A -weighted Sound Level Time Histories Conceptually. the citivalont sound lend can be a rp eased xs= Toted Simnel Energy)
tero {c) 104091x( Time Penal
:FLDiaRAL TI .MIT 4DNIANl TRATION 713
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TRANSIT NOIRE AND VIBRATION It1PACT ASSESSMENT f1ANUAL
Maihernaiinally. the equation Is as follows:
1 CL /tDJ
Lrg(t) = 1{7iu�tu(T Ll] )
ea
where
L.*0 = equr ratent sound lewd of tie period "t", dBA
T = time period. sec (3600 for an hourly I ,ti
X = number of samples, sec (]600 for an hourly
L =index of summation
Li individual A -weighted sound level. dllA
The equattan above can be rewritten as follows for a one -hoar time period:
14.,1 (1h) = to[Totad Sound Energy en 1 fir] — 35.dt
where
35,6 = numerical adjustment for a time period of I hour ( I Olog, 4(t)' Eq. B-7
The sound energy is totaled over a full hour (3600 seconds) and is accumulated for all noise events during that hour_ When computing the equivalent sound level for a time period other than one hour, T IS modified in the equation to the duration of the time period in seconds. The numerical adjustment (35 6) accounts for time period or intermtt. In this case, one hour.
An alternate way for computing I. a.rfor a series of transit -noise events using sound exposure levels can be expressed conceptually as follows:
L Ttldra rEtiergvStainof' 35.6
ey{1h _' .(ha (IJ'!SELs )—
Mathematically. the equation is as follows:
where
a
LrF(t) ® 1fllttA,u( 1flls't;llaf)
r=,
1. ,
T
SEL
= equivalent wound level of Lune peifrsd "C. dldA
tirne period. sric (3600 for an hourly L„r,iw l
= number of sample_ sec 13dOI) for an hourly L-wiina
iride?Q of summation
= individual sound ergrosure levee dBA
Eq, B-1!
I -Curly is adopted as the measure of cumulative noise impart for Wort-risldentlal land uses (those not Involving sleep) because
• Cori elates well with speech Interference In conversation aril on the telephone as well as interruption of TV, ratio, and music eryoyrnent
■ Increases with the duration oftransit events;
▪ Accoursts far the number of transit eventsover the hour, which is also Important to people's reactions; and
F DERAL TI AN'3IT r7.DNUNETRATIGI'.i :
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TI APISIT NOISE AND VIBRATION It'1PACT ASSE SMENT I1ANUAL • Is used by the Federal Highway Adrninvstratlan In assessing highway -traffic nuke mnpact-(Thus. this noise metric can be used for directly cannoning and contrasting highway, transit_ and multimodal alternatives},
B.1.4.5 Day -Night Sound Level (Ld,,): 24 -Hour Exposure from All Events
The metric for cumulative 24 -hour exposure is the Day -Night Sound Level, IA abbreviated hate as G.
It is a single, A -weighted decibel value that acc<xants for total sound enl gy from all sound sources Doer 24 hours and is eaccressed in the unit. dBA. Events bet..eel _ I 10 p.m. and 7 a.m. are increased by 14 dB to woo LIM for pimple's greater nighttime sensitivity to noise, Figure B- I I shows examples of typical L s, both for transit and non -transit sources, ranging from 50 to 04 dB. where 50 is considered a quiet 24 -hour period acrd 90 a loud 24 -hour period Note that these Ld,,,'s depend upon the number- of events during, day and night separately. including each event's duration, which is affected by vehicle speed.
Tilisik Se sIetra
Ganunaler T. sal worth ft, r , MI6 itch
tam < ei can
IS Gay. 3 Ngn1
nail T,anan of 46 nrus
6 -Car R t
:WO NV.. I6 Nam
cm..., Tram ae # mph
tucn . 6 Cars
15 Cray- i NyrYl
nail Tams,' p%at4t rrWlrir
trrrm
tee Dept Itl Nrpttt
All al so It
cY
6s¢kiitainttl Hodge
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cont_-
Daronta, env
- ' Wane llnay" tlrnan IL=
- 'K le-IAb*Roe r* erii
- Sow** iMalldaraterArga
SeniW'myeal t ww *es
Figure B- I I Typical Lan's
An example of sound level variation over 24 Burs is visualized in the bottom frame of Figure IB I 0J. The area under the carve represents the receiver's noise exposure over the 24 hours. Note that some vehicle passbys occur at night, when the background noise ,s typl ily lower and the IQ dB adjustment is appl red_
Conceptually. the day -night level can be expressed as:
L — eii__Total Sound Ene°r'rg9'n„), + fne1,Y,„ X Total Soloul ErnarNJi',va, a e,, 14J v, f!i 'T6Trze Periocllaaay (secmtzrs) Time Period',yror (seconds) FfDERAJ: TRAMIT ADNVINETFIATN N I 4
Pale 514 of 548 H Comment Letter 01
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Mathematically, the equation Is as fclicyvvs:
k M
Lay, = 10 gsu(l t, x 10(id.oell ) 4-1 Ci x 10({ i-in,„0n)!tu)) Ti i Try r_1
= cumulative, ?4 -hoer expuxure (diy.rIght sound le d rliBA = time period during thedame, between 7 a, nn. and 14 ip.m. see (54,[44) = number of samples during the daytime (54, 4)
= index of summation
= time inters -rid measurements in seconds ( I )
individual A -weighted sound level during the daytime, dI5A = time period during the nighttime, between 10 p.m. and 7 p.m. sec (32.400) number of samples during the nighttime (2,400}
index of summation
= time interval of measurements. vat ,t 1)
= individual A -weighted sound level during the nighttime, dISA = nightumrnoise. adltwtment ( 10 d6)
The equation above can be rewritten as follows:
L�fr ± 7 0iergToli 0.5 • Taut Emend EmerRynay ) 4' (4' n.„„it u • Ted ai Sound ErierFl3'sok4)I 40.4 The sound energy is totaled over a full 24 h+xrs, and the sound ever r is accumulates from all noise events daring that time perlerd. T h.e numerical adjustment (494) accounts for time period of Interest in this €-ase, 24 halos,
An alternative way of computing Li. front twenty-four hourly L.anro's can be expressed conceptually as follows;
Energy stem o f Energy SUM of
dayhrie, hourly Legs aal r, • nighttin , hourly Legs)
Ld„ = iGdor_lio( )
Time period (seconds)
The equation above can he rewritten as'
Energy sure of Energy son of
cluytime, hourly Legs + {nod f,n ` nigh t tr mr, hourly Legs} 100910( 6400
3640)
The equation abcwe can be reduced further and rewritten as Energy slim of Energy stem of
rlrr = 1f]ltigto(drrytinte, hglirty Le ,' + �rtaUP,a * nighttime, hourly Legs) — 13.a Eq. 6- I 0
(FEDERAL AtiMiNt5TRATK3hl 31S
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Li, due ter a series of transit-0wsse events ean also be computed In urns of SEL The equation below assumes that transit noise dominates the 21 -our noise ennvironment, where nighttime SELs are increased by ID dB before totaling:
Energy stun of Energy stem o f
Ldn — lai ngtutatl cloyrtime SELs + (nId1.a • all niuhttime SEL -1) 49,4 Eq.'8-I I
Li, Is adapted as thre miasur ni cumulative noise Impact for residential land tales (those irmslvrrag sleep), becarse rt:
• Correlates well with the results of atritudinal surveys of residential noise impact • Increases with the duration of transit events
• Accounts for the number of transit events over the full twenty-four hours • Accounts for the Increasers sensitivity to rxrlse at irrlghi, when most people are asleep • Allows composite measurements to capture ail sources of corrrimrtity noise combined • Allow quantitative comparison of transit noise with otter community noiste • k the designated i nitric of choice of otlxa- Federal agencies (e.g., HUD, FAA and EPA) and has wide Viterrsatlanai acceptance
FEDERAL TI AMIT AL7MNN75TFRATIGN 316
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Appendix C: Background for Transit Noise Impact
Criteria
The noise criteria presented in Section 4. I of this marital have beerr developed based on well. documented criteria and research an human response to community noise, The primary goals in de're=Ioping the noise criteria were to ensure that the impact limits are firmly roweled in scientific stuff, realistically based an noise levels assra sated with row Irenat prefects, and represent a reasonable balance between coururiunIty benefit and protect casts. This appendix provides background information an the development of these criteria.
C. I Relevant Literature
The following is an annotated fast of the documents that are particularly relevant to the noise impact criteria;
I. U.S. EPA's "Levels Document"i7e
This report identifies noise levels consistent with the pretettirtn of public health and welter e agalest hearing loss, anrroyarrre and activity interference. It hues been used as the basis of numerous community noise standards ,arsd ordinances.
1 Committee on Hearing, Bioaco usti6 and Riomechanic's (CHAS&) Worldng Group 69, "Guidelines for Preparing Environmental Impact Statements on Noise"ggr This report was the result of deriberations by a group of leading acoietical surientists with the goal +af devek ping a t i k rm natirnzal 1110114d fvr Heise impart assessor re Afth ngh the CI-IARA's P' oposed approaeh lies tat been adopted, the report serves as an aerelleret resource documenting research lie noise effects. It provides a strong scientific basis for quantifying impacts In terms of lee
3_ America, Public Tiransportation Association (APTA) Guidelines for Design of Rapid Transit Facilities' re
The noise and vibration sections of the APTA Guidelines have been used successfully in the past for the deSign cf rail tr iner facilities. The APTA Guidelines include criteria for acceptable community noise and vibration, Experience has shoo that meeting the APTA Guidelines will usually result In acceptable rartlse levels; kart the metric used In the APTA Guidelines is not appropriate for environmental assessment parrposes,
The APTA Gii deliree criteria are in terms of L. for cQrrventicnel RRT vehicles, and they cannot be used to romper among different Boucles d trarr5ltSince the AFTAG idelrnes are expressed in terms of maximum parssby noise, they are not sensitive to the frequency or duration of noise events for transit modes other than conventional FtRT operations with S to 10 minute headways. Therefore. the APTA criteria are questionable far assessing the nose impact et other transit roodis that differ from conventional rapid transit with respecr to source emission levels and vet -tiring charactertstres (e.g, commuter rail, AGT, acid variety of bits projects).
A. Synthesis of Social Surreys on Noise Annoyanc+ean
in 1978, Theeder- J_ Schulte, an Internaattonaity known acoustical scientist, synthesised the results of a large number of social surreys concerning annoyance dire to transportation noise, A group of these surveys were remarkably consistent and the author proposed that their average $LDERALTRAMITADNONt5TIYATIt hd 31?
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results be taken as the best available prediction of trampartatbr n noise annoyance. This synthesis has received essentially unanimous acceptance by acoustical scientists and engineers, The "universal" transportation response curve dervelriie J by Schultz (Figure 3-7) shows that the percent of the pif'r ilation highly 3nnryed by ItY -HriSportatIOn noise Increases from zero at an La", of approximately 50 dBA to 00% when La, Is approximately 90 dBA_ Most importantly. this cu€we indicates that for the same increase In Le there is a greater Increase in the numbe of people highly annoyed al high noise levels than at low noise levels- For eMari pie; a. 5 dB increase at low ai ibierrt levels (40 - 50 dB) has less impart than at higher ambient levels (r°,5 - 75 dB), A recent update of the original researelr contatlnIng several railroad, transit and street traffic noise surveys, confirming tht shape of the cr'iglital Schultz curve 'Ilk
5. HUD's Standardst'h
HUD has developed noise standards, criteria, and guidelines to ensure that housing protects supported by HUD achieve the goal of a suitable living environment. The HUD acceptability standards define 65 d8 CL,a,) as the threshold fora normally unacceptable Irving environment (moderate Impact for FTA) and 75 dB (Lan) as the threshold for an unacceptable living environment (severe impact for FTA)
C.2 Basis for Noise impact Criteria Cures
The lower curve in Figure 4-2 represents the onset of moderate impact and is bused on the following considerations:
■ The EPA finding that a community noise level of La, less than or equal to 55 dBA is "requisite to protect public health and welfare with an adequate margin of s,*fety,"rni • The conclusion by EPA and others that a 5 dB increase in Lm, or I -40,i Is the minimum required for a change Iii community reaction.
• The research concludes that there are very kw people highly annoyed when the La. k 56 dBA, and that an increase in La" from 5Q dBA to 55 dBA results in an average of 2% more people highly annoyed (Figure 3-7),
The increase in noise level from an existing ambient level of 5O dRA to acrrnuhative level of SS dBA because of a project is found to cause minimal impact, with 2% of people highly annoyed, as described in the bullets above. This is considered the lowest threshold where impact starts to occur. Therefore, for an existing ambient noise level of 54 dllA the curve representing the onset of moderate impact is at 53 dBA, the combination of which yields a cumulative level of SS dBA by decibel addition. The remainder of the lower curve in Figure 4-2 was determined horn the annoyance curve (Figure 3.7) by allowing a fixed 2% increase in annoyance at other levels of wasting ambient noise_ As cumulatiee noise increases. the increment to attain the same 2% increase In highly annoyed people is smaller. While it takes a 5 -dB noise increase to cause a 2% Increase in highly annoyed people at an existing ambient noise level of SO dB, an increase of only I d6 causes a 2% inOlease of highly annoyed people at an existing ambient noise level of 70 dBA.
The upper curve in Figure 4-2 represents the onset of severe impact based on a total noise level, corresponding to a higher degree of impact The severe noise impact curve is based our the following considerations:
■ HUD defines an La, of bS as the onset of a normally unacceptable noise zone hirsoderate impact for FTA) in its environmental noise standards 01. FM considers that residential land uses are rrr]t compatible with noise environments wince La, Is greater than 65 dBA (20).
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■ An increase of 5 dB Ire Ls, or Leee, is commonly assumed as the minimum required Increase for a change in community reaction.
■ The research c€ reluKIes that an increase of 5 dE! in La, or Lurid represents a 6.5% increase in the number of people highly annoyed (Figure 3=7).
The irirease In noise level from an existing ambient level of 60 dBA to a turnulatlee level of 65 dBA caused by a project represents a change from an acceptable noise environment to the threshold of an unacceptable noise environment. This is considered the level at which severe impact starts to occur with a 6..5' increase in the reurnber of people highly ertrtayed as described In the bullets above Thereforre, for an existing ambient noise level ref fro dRA the curve representing the asset of severe impact is at 63 dBA the combination of which yields a cumulative level of 65 dBA by decibel addition.
The remainder of the upper curve in Figure 4-2 was determined from the annoyance curve (Figure 3-7) by allcwwing a feted increase of the 6,5% roue ease In annoyance at all existing ambient noise levels.
Both craves incorporate a maximum limit for the transit p•€rje€t noise ill nolsesensitive areas.
Independent of wasting noise levels, moderate Impact for- land use categories I and 2 is considered to occur whenever the transit Lr equals or exceeds 65 riBA and severe impact occurs whenever the transit lee equals or exceed 75 dBA. Tie absolute limits are intended to reytrictactivity interference caused by the transit project alone.
Both cureee also incorporate a iiraximrran linnet for cumulative noise increase at low existing roiee levels (below approximately 45 dEA). This is a conservative limit that reflects the lack of social survey data tin peoples reactions to noise at such low ambient levels. Like the FHWA approach in assessing the relative Impact of a highway protect, the transit noise criteria [(elude ude limits on noise increme of I 0 dB and 15 dB for moderate Impact and severe impact, respectively, relative to the existing noise level.
Note that due to the types of Farad use Included In category 3, the criteria allow the prefect name for category 3 sites to be 5 dB greater than lot category I and category 2 sites. This: difference is reflected by the offset in the vertical scale on the right side of Figure 4=2. Aside from active park which are clearly less sensitive to noise than category 1 and 2 sites. category 3 sites include primarily indoor activities- Therefore, the criteria account for some noise reduction] from the building strucurre.
C.3 Equations for Noise Impact Criteria Curves
The equations for the noise impact criteria curves shown in Figure 4-2 are included in this section.
These equations may be useful when performing the noise assessment methrxlnloj using spreadsheets. computes programs. or other analysis tools. Otherwise, such mathematical detail is gerkerally not necessary to implement the criteria, and direct use of Figure 4-2 is adequate and less time-consuming.
A total of four continuous curves are Included h the criteria, creating two threshold curs for moderate and severe impact lor category I acrd 2, and two €twv@s for category 3 (See Table C -I). Note that for each level of Impact, the overall curvets for categories 1 and 2 are offset by 5 de from category
3. 'Bile each curve is graphically continuous,, each one is defined by a set of three discrete equations.
These equations are approximately COntiropEA at the transition peaints- The following is a description of the three Niel -bore:
• The first equation in each se is a linear relationship. representing the portion of the curve in which the existing noise exposure is low. and the allowable increase is limited to PO de and 15 dB for moderate impact and severe impact, respectively, FEDERAL TRANSIT ADNIONISTRATre}N i I
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