TO: TRAFFIC AND TRANSPORTATION COMMISSION
FROM: MARIA B. TIPPING, CITY ENGINEER
DATE: MAY 23, 2024
Reviewed by:
City Manager: N/A
SUBJECT:
Title
BASE LINE ROAD AT TOWNE AVENUE TRAFFIC SIGNAL MODIFICATION - CITYWIDE TRAFFIC SIGNAL IMPROVEMENTS PROJECT
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SUMMARY
The intersection of Towne Avenue at Base Line Road has experienced a number of collisions over the past several years, with many involving collisions between the westbound left turn vehicles and the eastbound through vehicles. To address the collision pattern and improve the overall safety of the intersection, staff is moving forward with the implementation of a traffic signal modification. The modification will include the removal of the existing median along Base Line Road, at the east side of the intersection, and removal of the existing protective-permissive operation for east and westbound traffic to be replaced with a protected only green arrow phase.
At tonight’s meeting, staff is presenting an item to the Commission to address the addition of this traffic signal modification to the upcoming Citywide Traffic Signal Improvements Project.
RECOMMENDATION
Recommended Action
Staff recommends the Traffic and Transportation Commission receive and file the Base Line Road at Towne Avenue Traffic Signal Modification - Citywide Traffic Signal Improvements Project report.
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FINANCIAL REVIEW
The cost to prepare this staff report is approximately $866 and is included in the Community Development Operating budget.
Funding for the installation of the recommended improvements is included in the Capital Improvement Program Budget for 2022-2024, under the Citywide Traffic Signal Improvements Project.
ANALYSIS
The intersection of Towne Avenue at Base Line Road is a heavily used intersection with particularly high traffic volumes during the peak weekday commuter hours. The intersection lies directly north of the Interstate 210 freeway on/off ramps. The traffic signal at this location currently operates under a protective-permissive signal operation for the east-west directions. Originally, this traffic signal was installed by Caltrans when Base Line Road was under their jurisdiction.
The protective-permissive operation is often used at intersections where there are large volumes of traffic in one direction, and smaller traffic volumes in the opposing direction, which is the case for the Base Line and Towne intersection. With this type of traffic signal operation, both a protected and permissive phase are provided. With the protected phase, the left turning driver receives a green arrow indication, and the opposing through traffic is stopped with a red light. When the protected phase ends, a yellow arrow is displayed, followed by a green ball, permissive phase. Once the green ball indication is activated for the left turn, the opposing traffic receives a green light and the left turning traffic must yield to oncoming traffic. Westbound left turns are heavy during commuter peak hours. Currently, signage provided at the intersection alerts westbound drivers of the need to yield to oncoming traffic during the green ball phase.
At the Base Line Road and Towne Avenue intersection, a number of collisions have occurred between the westbound left turning traffic and the eastbound through movement traffic, many of which are associated with the permissive phasing. Additionally, the vertical curvature coming eastbound from Live Oak Bridge also contributes to the intersection’s dynamics.
Staff commissioned a traffic study for this location, performed by the City’s traffic engineering consultant, Advantec Consulting Engineers, to determine the most effective method to reduce the number of collisions at this intersection. The traffic consultant evaluated collision data provided by the Claremont Police Department (CPD), along with a review of the existing conditions. The findings of the traffic study recommend the removal of the protective-permissive traffic signal operation for the east and westbound left turns and replacement of this traffic signal operation with protective only green arrow phase. This new phasing should help reduce the left turn collisions at this intersection. This new operation also separates the pedestrian phase from the left turning vehicles.
The attached summarized collision data used for this study (May 2019 through August 2023), as provided by the CPD, supports the recommended improvements.
To address the permissive left turn collision pattern present at this location and to improve the overall safety of this intersection, staff will move forward with the recommended traffic signal modification, which will be included in the upcoming Citywide Traffic Signal Improvement Project that is part of the City’s Capital Improvement Program (CIP). The modification will include the removal of the existing median along Base Line Road, at the east side of the intersection, and removal of the existing protective-permissive operation for the east and westbound traffic, to be replaced with a protected only green arrow phase.
As next steps, staff will update the plans and specifications for the upcoming Citywide Traffic Signal Improvement Project, anticipated to be considered for award by the City Council by July 2024. Staff hopes to see these improvements completed by the end of the year pending any potentially long lead times for the signal equipment needed for this project.
CEQA REVIEW
This item is not subject to environmental review under the California Environmental Quality Act (CEQA).
PUBLIC NOTICE PROCESS
The agenda and staff report for this item have been posted on the City website and distributed to interested parties. If you desire a copy, please contact Commission Secretary, Carrissa Roque at croque@ci.claremont.ca.us.
Submitted by: Prepared by:
Maria B. Tipping, P.E. Vincent Ramos
City Engineer Associate Engineer
Attachment:
Summarized Collision Data and Vehicle Code Definitions