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TASK 3.2.2 - TECHNICAL MEMORANDUM SUMMARIZING POTENTIAL
ROADWAY CONFIGURATION TRAFFIC ANALYSIS
TO: Carolyn Mamaradlo (San Mateo County Transportation Authority), Douglas Kim (Town of Atherton) FROM: Kay Cheng (WSP), Akshaey Sabha (WSP)
SUBJECT: Technical Memorandum Summarizing Potential Roadway Configuration Traffic Evaluations DATE: February 5, 2025
INTRODUCTION
This memorandum presents a technical analysis of potential roadway configuration concepts along El Camino Real between Oakwood Dr and Valparaiso Ave, focusing on traffic operations under 2025 conditions. The objective is to evaluate three proposed concepts—a 6-lane, 5-lane, and 4-lane configuration with separated and/or striped bike lanes-and their impacts on multimodal accessibility, intersection performance, corridor travel time, and arterial speed. Key improvements such as new signalized intersections, HAWK signals, and pedestrian enhancements were incorporated to optimize network operations. This analysis provides data- driven insights to support decision-making for enhancing mobility and safety along the corridor.
1. FUTURE CONDITIONS (2025) ANALYSIS
This analysis considers the anticipated traffic demand for 2025 and evaluates three potential concepts within the corridor. These concepts were developed to address key objectives, including improving multimodal accessibility and enhancing overall traffic efficiency.
The following concepts were analyzed:
1. No-Build Configuration: This scenario maintains the existing corridor geometry with no project-specific geometric modifications. Only background infrastructure improvements and signal timing changes are included.
2. 6-Lane Configuration with Striped Bike Lane: This alternative maintains six travel lanes and incorporates a dedicated bike lane, striped from vehicular traffic.
3. 4-Lane Configuration with Separated Bike Lane: This alternative reduces the travel lanes to four, allowing additional space for a separated bike lane.
4. 5-Lane Configuration with Separated/Striped Bike Lane: This alternative provides a middle ground, maintaining five travel lanes and adding a separated or striped bike lane.
Key adjustments to the corridor for all three concepts provided by the City of Atherton include:
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1. Selby Lane Intersection Signalization: Selby Lane was upgraded to a signalized intersection to enhance safety and operational performance for minor street traffic movements.
2. Watkins Avenue Intersection Signalization: A new traffic signal was installed at Watkins Avenue to better manage traffic flow and reduce delays.
3. Stockbridge Avenue HAWK Signal Installation: A High-Intensity Activated Crosswalk (HAWK) signal was installed at Stockbridge Avenue to improve pedestrian safety.
4. Encinal Avenue Intersection Improvements: A new south-leg crosswalk was added to the Encinal Avenue and El Camino Real intersection, enhancing pedestrian connectivity and safety.
5. Median Refuge Islands: Median refuge islands were installed at Alejandra, Almendral, and Isabella intersections to provide safer crossing opportunities for pedestrians.
The traffic demand data for this analysis was derived from the C/CAG-VTA model, by processing the existing condition demand, applying a growth rate, and balancing the volumes to generate demand input. Adjustments were made to the network signal timing to optimize traffic flow along El Camino Real and ensure efficient clearance for vehicles on minor streets.
The evaluation results for each alternative will include performance metrics such as Level of Service (LOS), movement delay, 95th percentile queue lengths, total travel time, and average speeds. These results will be discussed in detail in subsequent sections to identify the most effective alternative for meeting the corridor's multimodal and traffic flow needs.
METHODOLOGY
To accurately represent Year 2025 traffic conditions, WSP processed collected AM and PM peak hour vehicle, pedestrian, bicycle, heavy vehicle, and bus volumes. Synchro 12 or Highway Capacity Software was used for the analysis, incorporating peak hour volumes, including peak hour factor, heavy vehicle percentage, pedestrian volume, bicycle volume, and vehicle volume.
The analysis adhered to the Highway Capacity Manual (HCM) guidelines, with results exported using the HCM 7h Edition where applicable, or HCM 2000 results if necessary. Key performance indicators (KPIs) such as Level of Service (LOS), movement delay, 95th percentile queue, total travel time, and average speed were evaluated to assess the operational efficiency of intersections and roadway segments.
2025 CONDITION RESULTS
INTERSECTION LOS AND DELAY:
An analysis of the Level of Service (LOS) and movement delay was conducted for 2025 conditions, comparing the No-Build scenario with the three proposed build concepts (Concept #1, Concept #2, and Concept #3). The analysis utilized the AM and PM peak hour turning movement volumes for each scenario. The results for signalized intersections and HAWK beacons under future conditions are summarized in Table 1 and 2, highlighting the operational performance differences between the No-Build and the three concepts for both AM and PM.
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INTERSECTION NO BUILD Concept! Concept2 Concept 3 NO BUILD Concept 1 Concept 2 Concept 3 6-LANE 4-LANE 5-LANE 6-LANE 4-LANE 5-LANE
WITH ECR DELAY LOS
DELAY DELAY DELAY LOS LOS LOS
Oakwood Dr 26 26 28 28 C C C
Selby Ln 19 19 35 22 B B C C
Fifth Ave 26 26 28 25 C C C C
Stockbridge Ave A A A A
Almendral Ave 7 A A A A
Fair Oaks Lane 17 17 29 B C C
Isabella Ave A A A A
Watkins Ave 17 17 15 27
Alejandra Ave 1 A A A A
Encinal Ave 23 23 33 23
Valparaiso Ave 27 27 57 27 C C D
Note:
Delay Units is in seconds
Table 1.: AM Peak Hour Delay and LOS Comparison for No-Build and Concepts #1, 2, and 3 The analysis of AM peak hour intersection operations indicates the following key performance outcomes for the No-Build and alternative scenarios:
• Oakwood Drive: Delay remains consistent at 26 seconds across the No Build and Concept #1 scenarios, with minor increases observed in Concepts #2 and 3 (28 seconds). LOS remains stable at C.
• Selby Lane: Delay remains at 19 seconds in Concept #1 but increases to 35 seconds in Concept #2 and 22 seconds in Concept #3. LOS is B in Concept #1, with Concept #2 experiencing a drop to C.
• Fifth Avenue: Delay remains largely consistent across all scenarios, ranging from 25-28 seconds, with LOS holding at C.
• Stockbridge Avenue, Almendral Avenue, Isabella Avenue, and Alejandra Avenue: These intersections continue to operate efficiently at LOS A, with minimal delays across all concepts.
• Fair Oaks Lane: Concept #1 maintains the lowest delay at 17 seconds (LOS B), while Concepts #2 and 3 experience increased delay at 29 seconds (LOS C). • Watkins Avenue: Delay remains at 11 seconds for Concept #1 but rises to 15 seconds in Concept #2 and 27 seconds in Concept #3. LOS remains at B for Concepts #1 and 2 but drops to C for Concept #3.
• Encinal Avenue: Delay remains stable at 23 seconds for Concepts #1 and 3, with Concept #2 experiencing an increase to 33 seconds. LOS remains at C across all scenarios.
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• Valparaiso Avenue: Concept #1 maintains the same delay as the No-Build scenario at 27 seconds (LOS C), whereas Concept #2 experiences a substantial increase to 51 seconds (LOS D), with Concept #3 holding at 27 seconds (LOS C).
Among the three concepts, Concept #l performs most efficiently in minimizing vehicle roadway delays, followed by Concept #3, while Concept #2 experiences the highest delays at key intersections. However, all concepts remain within acceptable operational limits, as none exceed LOS E, ensuring effective corridor traffic flow during the AM peak hour period.
INTERSECTION Concept 1 Concept 2 Concept 3
WITH EL CAMINO NO BUILD Concept 1 Concept 2 Concept 3 NO BUILD 6-LANE 4-LANE 5-LANE 6-LANE 4-LANE 5-LANE
DELAY LOS
REAL DELAY DELAY DELAY LOS LOS LOS
Oakwood Dr 10 10 23 10 A A C A
Selby Ln 14 14 16 19
Fifth Ave 35 35 62 34 C C E
Stockbridge Ave
Almendral Ave A
Fair Oaks Lane 18 18 31 26
Isabella Ave A
Watkins Ave 6 6 50 14 A D
Alejandra Ave A
Encinal Ave 15 15 27 15 B
Valparaiso Ave 24 24 52 33 C C
Note:
Delay Units is in seconds
Table 2: PM Peak Hour Delay and LOS Comparison for No-Build and Concepts #1, 2, and 3 The analysis of PM peak hour intersection operations indicates the following key performance outcomes for the No-Build and alternative scenarios:
• Oakwood Drive: Delay remains at 10 seconds for Concept #1 and Concept #3, while Concept #2 experiences an increase to 23 seconds. LOS remains at A for Concepts #1 and 3, while Concept #2 operates at C.
• Selby Lane: Delay is consistent at 14 seconds for Concepts #1 and 2, increasing to 19 seconds in Concept #3. LOS remains at B across all scenarios.
• Fifth Avenue: Concept #2 experiences the highest delay at 62 seconds (LOS E), while Concept #3 reduces the delay to 34 seconds, maintaining LOS C. • Stockbridge Avenue, Almendral Avenue, Isabella Avenue, and Alejandra Avenue: These intersections maintain LOS A across all concepts, with minimal delays.
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• Fair Oaks Lane: Concept #1 experiences 18 seconds of delay (LOS B), while Concepts #2 and 3 see increased delays of 31 seconds and 26 seconds, respectively, both operating at LOS C. • Watkins Avenue: Delay remains at 6 seconds in Concept #1 but increases significantly to 50 seconds in Concept #2 (LOS D) and 14 seconds in Concept #3 (LOS B). • Encinal Avenue: Concept #1 maintains 15 seconds of delay (LOS B), while Concept #2 increases to 27 seconds (LOS C), with Concept #3 maintaining 15 seconds (LOS B). • Valparaiso Avenue: Concept #1 holds steady at 24 seconds (LOS C), while Concept #2 sees an increase to 52 seconds (LOS D) and Concept #3 experiences 33 seconds (LOS C).
During PM peak hour period, Concept #1 has the lowest intersection delay, followed by Concept #3, while Concept #2 experiences the highest delays at key intersections. Fifth Avenue operates at LOSE during Concept #2, while all other intersections remain at LOS Dor better. Despite these differences, all concepts function within acceptable limits, ensuring effective corridor traffic flow.
The analysis of corridor performance focuses on two key metrics: travel time and arterial speed for the northbound (NB) and southbound (SB) directions during the AM and PM peak hours.
CORRIDOR TRAVEL TIME AND ARTERIAL SPEED:
These metrics provide insights into the operational efficiency and congestion levels along the corridor under the three proposed geometric configurations: 6-lane, 4-lane, and 5-lane designs.
Travel time measures the total time required to traverse the corridor, accounting for delays at intersections and along the roadway. Arterial speed reflects the average travel speed achieved, incorporating both moving and stopped times. A recent speed survey found the critical speed and average speed for traffic is 38 and 35 mph, respectively, under free flow conditions on El Camino Real.' The results are summarized in the following table, highlighting the performance differences across the three concepts and identifying potential impacts on traffic flow and efficiency.
California Department of Transportation, District 4; Report of the Engineering and Traffic Survey; December 19, 2024. Critical speed is the speed at or below which 85% of vehicles travel under free-flow conditions while average speed is the mean of all vehicles traveling during a specific period. Speeds reflect 1.39-mile stretch between Stone Pine Lane to 100 feet north of Berkshire Avenue.
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Table 3: Comparison of Corridor Travel Time and Arterial Speed Corridor Performance
Travel Time (min) Arterial Speed (mph)
Lane te Concept 3 No- Concept Concept : Concept :
5-Lane Geo Build 6-Lane Ge +-Lane Gec 5-Lane Gec
NB 5.8 5.8 6.1 5.9 20.3 20.3 19.2 19.7
AM
SB 5.5 5.5 7.0 6.9 20.7 20.7 16.3 16.5
NB 5.5 5.5 6.3 5.7 21.2 21.2 18.6 20.6
PM
SB 5.2 5.2 5.2 5.1 21.9 21.9 22.1 22.3
The results highlight the travel time and arterial speed performance under the three proposed configurations across AM and PM peak periods:
6-Lane Configuration (Concept #1):
1. Travel times remain unchanged compared to the No-Build scenario across all time periods. Northbound and southbound travel times during both AM and PM peaks remain consistent, indicating that this configuration does not introduce additional delay.
2. Arterial speeds remain the same as the No-Build scenario, with no changes observed in northbound or southbound directions across AM and PM peaks.
This configuration maintains the most efficient traffic flow, ensuring no increase in congestion or delay while preserving the existing operational conditions. 4-Lane Configuration (Concept #2):
3. Travel Time: The northbound AM peak experiences a 5% increase, rising from 5.8 minutes to 6.1 minutes. The southbound AM peak sees the most significant increase, with a 27% rise, reaching 7.0 minutes from 5.5 minutes. During the northbound PM peak, travel time increases by 14%, rising from 5.5 minutes to 6.3 minutes, while the southbound PM peak remains unchanged at 5.2 minutes
4. Arterial Speed : The northbound AM peak speed decreases by 5%, dropping from 20.3 mph to 19.2 mph. The southbound AM peak speed sees a 21% decline, reducing from 20.7 mph to 16.3 mph. In the northbound PM peak, speed decreases by 12%, going from 21.2 mph to 18.6 mph, while the southbound PM peak speed increases slightly by 1%, reaching
22.1 mph.
This configuration results in the highest travel time increases and the largest arterial speed reductions, particularly affecting the southbound AM and northbound PM periods, indicating higher congestion and slower traffic movement compared to the No-Build scenario. 5-Lane Configuration (Concept #3):
5. Travel Time: The northbound AM peak sees a 2% increase, with travel time rising from 5.8 minutes to 5.9 minutes. The southbound AM peak experiences a 25% increase, increasing from 5.5 minutes to 6.9 minutes. During the northbound PM peak, travel time rises by 4%, reaching 5.7 minutes from 5.5 minutes, while the southbound PM peak sees a slight decrease of 2%, dropping from 5.2 minutes to 5.1 minutes.
6. Arterial Speed : The northbound AM peak speed decreases by 3%, from 20.3 mph to 19.7 mph. The southbound AM peak speed declines by 20%, reducing from 20.7 mph to 16.5
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mph. The northbound PM peak speed drops by 3%, going from 21.2 mph to 20.6 mph, while the southbound PM peak speed increases slightly by 2%, reaching 22.3 mph.
This configuration presents moderate travel time increases compared to a No-Build scenario and smaller reductions in arterial speed compared to the 4-lane alternative. While it introduces some delays, it maintains better overall flow and efficiency than the 4-lane configuration.
Key Impacts:
• The 6-lane configuration maintains the fastest travel times and highest speeds, with no changes compared to No-Build
• The 4-lane configuration results in the longest travel times and largest speed reductions, particularly in southbound AM and northbound PM, indicating greater congestion. • The 5-lane configuration presents a middle ground, with moderate impacts on travel time and minimal reductions in arterial speed, making it more efficient than the 4-lane option.
CONCLUSION
The analysis evaluates the operational performance of the three proposed roadway configurations compared to the No-Build scenario, focusing on intersection delay, travel time, and arterial speed
6-Lane Configuration (Concept #1) provides the most consistent traffic operations, with no increase in travel time or reduction in arterial speeds. This configuration ensures efficient traffic flow while integrating multimodal improvements without additional delays. • 4-Lane Configuration (Concept #2) demonstrates acceptable intersection operations, with most locations maintaining LOS D or better. However, travel time is notably higher, particularly in the southbound AM at Atherton Ave and northbound PM at Fifth Ave, where a 27% increase in SB AM travel time and a 21% decrease in SB AM arterial speed are observed. This suggests a trade-off between multimodal accessibility and vehicle travel time efficiency.
5-Lane Configuration (Concept #3) presents a balanced approach, with moderate travel time increases and smaller reductions in arterial speed compared to the 4-lane alternative.
While some delay increases are observed, this configuration provides better overall traffic flow than the 4-lane alternative, while still accommodating multimodal needs.
KEY FINDINGS:
1. The 6-lane configuration maintains efficient traffic flow with no increase in congestion, making it the most effective in minimizing travel time and maintaining speed.
2. The 4-lane configuration performs well in terms of intersection delay but experiences higher travel times, particularly in SB AM and NB PM, indicating increased congestion in those periods.
3. The 5-lane configuration serves as a middle ground, balancing traffic efficiency and multimodal considerations, with moderate travel time increases and manageable impacts on arterial speed.
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This analysis underscores the trade-off between vehicle multimodal accessibility and vehicle speed and delay. The 6-lane configuration retains current vehicular conditions, the 4-lane configuration prioritizes non-motorized safety while introducing additional travel time, and the 5-lane configuration provides a middle ground between these objectives.