CC - Item 7E - Proposed Traffic Signal Improvements - San Gabriel Boulevard at Walnut Grove AvenueROSEMEAD CITY COUNCIL
STAFF REPORT
TO: THE HONORABLE MAYOR AND CITY COUNCIL
FROM: JEFF ALLRED, CITY MANAGER
DATE: OCTOBER 25. 2011
SUBJECT: PROPOSED TRAFFIC SIGNAL IMPROVEMENTS —SAN GABRIEL
BOULEVARD AT WALNUT GROVE AVENUE
SUMMARY
The Traffic Commission reviewed a request to evaluate traffic flow at the intersection of
San Gabriel Boulevard and Walnut Grove Avenue. Motorists traveling through this
location sometimes experience delay, traffic congestion, and some vehicle conflict.
After visiting the site, it was recommended that short-term traffic signal improvements
be made to improve the traffic conditions at the location. Additional long -term
improvements will be pursued but will also require coordination with Caltrans due to the
nearby freeway onramp and its close proximity to this intersection. The Commission
concurred with this recommendation.
Staff Recommendation
It is recommended that the City Council approve the Traffic Commission's
recommendation and authorize staff to make minor signal modifications, install "cat -
track" lane striping, and install "Do Not Block" signs at the intersection of San Gabriel
Blvd. and Walnut Grove Ave.
DISCUSSION
City staff received a request to evaluate traffic conditions at the intersection of San
Gabriel Blvd. and Walnut Grove Ave. In August 2011, observations and a study were
conducted at this intersection and the nearby intersection at SR -60 and San Gabriel
Blvd. (just adjacent to Charlie Brown's). Traffic counts of turning movements were
conducted at each intersection during weekday peak morning and afternoon times.
These counts, along with existing intersection lane configuration and signal phasing
information, were analyzed using traffic engineering /analysis software to determine
existing intersection performance, traffic operational problems, and to develop potential
improvement measures to mitigate these problems.
The traffic engineering investigation and analysis conducted at the two intersections
identified potential traffic problems that could be addressed by modifying existing signal
operations and by restricting certain permitted movements at these intersections during
traffic signal phases. Once implemented, these improvements are expected to
significantly reduce undue delays as well as the potential for accidents.
APPROVED FOR CITY COUNCIL AGENDA: $ f EM • • 0 O -- "
City Council Meeting
October 25, 2011
Pace 2 of 3
The proposed improvement measures are described further below:
San Gabriel Boulevard at Walnut Grove Avenue
The City controls all signal operations at this intersection. As a result, the adjustments
listed below can be made and will not impact the adjacent intersection controlled by
Caltrans.
• Prohibit northbound right turns (from northbound San Gabriel Boulevard to
northeast bound Walnut Grove Avenue) only during the eastbound split phases
(when vehicles exit the gas station / Carrow's driveway). This right -turn restriction
will help remove potential vehicle conflicts and will include a red arrow that will
prohibit turns only when vehicles exit the Carrow's driveway.
For instance, a vehicle will approach the intersection to exit Carrow's or the gas
station. This will alert the traffic signal to activate a signal phase to allow vehicles
to exit the shopping center onto San Gabriel Blvd. or Walnut Grove Ave. When
these vehicles receive a green light, opposing traffic will not be allowed to turn
right from northbound San Gabriel Blvd. to northeast bound Walnut Grove Ave.
• Install cat -track striping (dashed lane markers) across the intersection to better
delineate lanes.
• Install "Do Not Block" signage on all traffic signals.
• Replace signal loop detectors and update traffic signal equipment to improve
traffic signal timing.
San Gabriel Boulevard at SR -60 Freeway Westbound Ramps
Caltrans controls all signal operations at this intersection. As a result, the adjustments
listed below will need to be coordinated through the Caltrans District 7 Office and will
require additional review time.
• Provide split phases for the eastbound and westbound movements; by
reconfiguring signal phasing so that an exclusive phase is provided only for
eastbound (left -turn, right -turn and through) movements, and another exclusive
phase for westbound (left -turn, right -turn and through) movements. Currently, all
eastbound and westbound movements are allowed during one single phase,
creating confusion, delay and potential for conflicts), and
• Prohibit westbound right turns (from off -ramp to northbound San Gabriel
Boulevard) during the eastbound split phases.
• Improve directional signage at the freeway off -ramp.
City Council Meeting
October 25, 2011
Page 3 of 3
Due to the shared operation of this intersection with Caltrans, these signal modifications
will need to be shared, analyzed, and approved by Caltrans officials. Due to these
coordination issues, it is thought that these proposed improvements will take a longer
time period to implement.
An overhead map view of the area, intersection analysis and traffic counts are includes
for further review.
Sub by:
CHRIS MARCARELLO
Public Works Director
Attachments:
1. Overhead Map
2. Intersection Traffic Counts
3. Detailed Analysis
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Intersection Performance and Safety Analysis
San Gabriel Boulevard at SR -60 Westbound Ramps and Walnut Grove
Avenue, City of Rosemead, California
A field investigation was conducted and traffic counts (of AM and PM peak period turn
movements) were taken during the third week of August, 2011 at the intersection of San Gabriel
Boulevard and SR -60 Westbound Ramps and at San Gabriel Boulevard and Walnut Grove
Avenue in the City of Rosemead. This report presents the results of this investigation as well as
an analysis of the intersection performance and traffic safety conditions. Traffic engineering
recommendations for improvements were also provided.
The summary of intersection traffic counts conducted during the AM peak period (7:00 AM to
9:00 AM) and the PM peak period (4:00 PM to 6:00 PM) on Thursday, August 18, 2011 (a
typical weekday) are attached to this report. Based on these counts, it has been determined that
both of these intersections show an AM peak hour between 7:45 AM and 8:45 AM, and a PM
peak hour between 5:00 PM and 6:00 PM.
An accident history analysis for the last three years (2008 through 20 10) shows that there have
been a total of 15 accidents reported at or near Walnut Grove Avenue /San Gabriel Boulevard,
and 1 accident reported at San Gabriel Avenue /SR -60 Freeway (see the attached accident
history). At least 3 of these accidents are directly related to the signal conditions and others are
likely to be related to intersection configurations and/or speeding.
San Gabriel Boulevard is posted with a speed limit sign of 45 miles per hour.
The intersections were analyzed using Synchro traffic analysis software to determine existing
level of service (LOS) and intersection delays under existing signal cycle and phasing for various
movements. Base on an observation of traffic safety conditions, it has been determined that
providing separate phases for eastbound and westbound movements (i.e., splitting the phases)
will improve traffic safety. The splitting of phases will result in movement of eastbound traffic
during an exclusive phase (when all other traffic will remain stopped). The same will apply when
westbound traffic will move during an exclusive phase. The results of intersection level of
service with existing and proposed signal phasing are presented in the table below. The details of
Synchro calculations are also attached.
Intersection
Peak Hour
Existin Condition
Proposed* Conditions
Delay, Sec. LOS
Delay, Sec. LOS
San Gabriel Boulevard @
SR -60 Westbound Ramps
AM
6.7
A
9.5
A
PM
9.1
A
15.9
B
San Gabriel Boulevard @
Walnut Grove Avenue
AM
7.8
A
9.4
A
PM
12.0
B
13.6
B
* Proposed Conditions include splitting of signal phases for eastbound and westbound
movements at both intersections.
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