GIBBONS/HIGH/FERNSIDE
INTERSECTION EVALUATION AND
TRAFFIC STUDY OVERVIEW
Exhibit 4
Intersection Traffic
Study
INTERSECTION SAFETY ISSUES
Long Crosswalks:
Over 70’ LongNo Signal Phase to
Protect Pedestrians:
Difficult to Cross
Gibbons Drive
High-Speed: Turns onto
Gibbons from High
Street have large radius
Confusing: Improper Left
Turns onto High Street
from Gibbons Drive
Complicated Layout: Many
Conflict Points, Including
Pedestrian and Bicycle Crossings
of High-Speed Slip Lane
INTERSECTION OPERATIONS AND SIGNAL PHASING ISSUES
Future Design Must
Accommodate Two-
Way Separated
Bikeway
5-Leg Intersection
Creates Complex Signal
Operation
No pedestrian signal
ALTERNATIVE A. REALIGN AND RESTRICT LEFT TURN
Description:
• Realigns Gibbons at High Street
• Restricts Gibbons exit to right only
on High Street
• Shortens long pedestrian crossings
• Reduces turn radius onto Gibbons
ALTERNATIVE B. REALIGN AND ALLOW LEFT TURN
Description:
• Realigns Gibbons at High Street
• Allows Gibbons exit right and left on
High Street with a new signal
• Shortens long pedestrian crossings
• Reduces turn radius onto Gibbons
ALT C. LOW-COST IMPROVEMENTS
Description:
• No change to Gibbons alignment
• Adds a pedestrian signal crossing
Gibbons Drive only in long-term
implementation
• Reduces turn radius onto Gibbons
with painted curb extension
INSUFFICIENT RIGHT OF WAY FOR ROUNDABOUT
Roundabout analyzed but not
recommended:
• Insufficient room for Gibbons leg
• Lengthened paths of pedestrian
and bicycle travel
• Non-traditional lane configuration
• Right-of-way impacts
TRAFFIC STUDY ANALYSES
Analysis 1
Intersection Safety
and Operations
Analysis 2
Neighborhood
Traffic Circulation
Analysis 1.
Intersection Safety
and Operations
INTERSECTION ANALYSIS KEY QUESTION
How well do the design alternatives improve safety and simplify traffic operations at Gibbons/High/Fernside?
Analysis takes alternatives in the context of the long-term Fernside Boulevard corridor design with the two-way bikeway.
ANALYSIS RESULTS: ALTERNATIVE A (TURN RESTRICTION)
Safety: Addresses Key Issues
• Shorter pedestrian crossings
• Slowed vehicle turn speed
• Simplified intersection layout reduces
number of conflict points
Operations: Minimal Change to Congestion
• Simplifies intersection with fewer signal
approaches requiring dedicated phases
• In the near term, reduces traffic congestion
• Allows for addition of bikeway with minimal
change to traffic congestion in long term
A
ANALYSIS RESULTS: ALTERNATIVE B (NEW SIGNAL)
Safety: Addresses Key Issues
• Shorter pedestrian crossings
• Slowed vehicle turn speed
• Simplified intersection layout
Operations: Severe Congestion in Long Term
• In the near term, makes traffic congestion
worse on High Street because of the
additional signal.
• With long term addition of bikeway, makes
traffic congestion on High Street much
worse, risking spillover onto other
neighborhood streets.
B
ANALYSIS RESULTS: ALTERNATIVE C (LOW COST)
Safety: Addresses Some Issues
• Slower vehicle turn speed
Operations: Severe Congestion in Long Term
• In the near term, traffic congestion would stay
the same with paint-only changes.
• With long term addition of bikeway, makes
traffic congestion on High Street worse
because of the additional pedestrian signal.
C
INTERSECTION ALTERNATIVES SUMMARY
Alternative Safety Congestion:
Near-Term
Congestion:
Long-Term
A
Improvement Improvement
Minimal Change
B
Improvement Worse Worse
C
Minor Improvement
No Change
Worse
Analysis 2.
Neighborhood Traffic
Circulation (with Alt. A)
TRAFFIC CIRCULATION ANALYSIS KEY QUESTION
What effect does the turn restriction
in Alternative A have on cut-through
traffic, and how will traffic
redistribute in the neighborhood?
Traffic circulation for Alternatives B & C not
studied because they don’t have a turn
restriction.
EXISTING NEIGHBORHOOD CIRCULATION
All streets inside the study area
are classified as Neighborhood
Local Streets:
• Target design speed 20 mph
• Target traffic volumes <1,000-
4,000 vehicles per day
• Neighborhood Greenway
targets <1,500 vehicles per
day
EXISTING ESTIMATED DAILY TRAFFIC VOLUMES
Neighborhood Local traffic
volumes <1,000-4,000*
vehicles per day
Neighborhood Connector
traffic volumes 4,000-
18,000* vehicles per day
*High end of target ranges are the
maximum capacity of each classification
Gibbons
2,200
Cornell
160
Bayo Vista
150
Fernside
8,600
GIBBONS DRIVE EXISTING TRAFFIC
31 mph
85th percentile speed
>55%
Northbound vehicles
cutting through
REDISTRIBUTION ANALYSIS
With the Alternative A left turn restriction, how will drivers who use Gibbons Drive today access High Street?
The analysis assumes redistribution through the
neighborhood based on:
• Distance
• Street characteristics
• Number of turns and stop signs
• Street parking occupancy
RESULTS: ALTERNATIVE A TRAFFIC REDISTRIBUTION
Santa Clara or Central
+5-10 vehicles
Southwood/Bayo Vista
+45-50 vehicles
Cornell Dr
+30-35 vehicles
Broadway/Tilden/Fernside: 0-5
Other Neighborhood Local Streets: 0-5
In the morning peak hour, 88
drivers turn left from Gibbons onto
High Street. The analysis assigns
them to other routes.
HOW DO DAILY TRAFFIC VOLUMES COMPARE WITH OTHER STREETS? 150
160
200
450
550
600
980
1400
1500
1800
2200
8600
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Bayo Vista Ave (before)
Cornell Dr (before)
Moreland Dr
Cornell Dr (after)
Pacific Ave
Bayo Vista Ave (after)
San Antonio Ave
Gibbons Drive (after)
Neighborhood Greenway Target
Clinton Ave
Gibbons Drive (before)
Fernside Blvd
Vehicles per Day
Traffic volumes on Bayo Vista and
Cornell would be higher than they are
now, but still on the low end for
Neighborhood Local streets in Alameda.