Signal Spotlight: Bristol Evaluation and Retiming of City-Owned Traffic Signals
The City of Bristol Public Works Department recently undertook a project to inventory and retime each of the city’s 36 signalized intersections. The goal of the project, which took approximately six months to complete (during the pandemic), was to create an inventory of the City’s traffic signal assets and to retime the signals to improve efficiency and reduce delay. Additionally, the project included training Public Works personnel to program the new signal timings into the controllers.
Much of the City’s traffic signal stock is over 20 years old, driving an increase in requests for maintenance. In recent years, the City worked to fully replace two signals in the downtown area. A few years ago, City staff noticed areas of congestion where the traffic signals were not operating as designed. The Public Works Department improved operations by installing video detection at 17 of the 36 signalized intersections to replace damaged, non-functioning loop detectors. The signal retiming project was the next logical step toward providing low-cost improvements to traffic signal operations and maintenance.
Public Works Director Ray Rogozinski notes that traffic signal retiming is one of the most cost-effective methods to improve traffic flow throughout a municipal roadway network. Indeed, according to NCHRP Synthesis 409: Traffic Signal Retiming Practices in the United States published in 2010, for most agencies traffic signal retiming costs $3,700 or less per intersection. A study of 26 projects in Texas showed an overall benefit/cost ratio of 38:1. A total of $1.7 million was spent among the projects, which resulted in average delay reductions of 19.4 percent, an 8.8 percent reduction in number of stops, and a 13.3 percent reduction in fuel consumption.
In the case of Bristol’s signals, the cost for the retiming study was $65,500 for 36 traffic signals, or $1,819 per intersection. This does not include the labor to reprogram each controller, which is expected to be performed by in-house forces. The Department plans to conduct spot evaluations after the retiming work is complete to assess the improvements in performance.
One recommendation of the inventory report produced as part of the project was a phased replacement of older traffic signals in the city’s downtown. In February, the City submitted a CMAQ application for a downtown signal system modernization project. The primary objective will be to improve traffic operations at six intersections in the downtown area to accommodate anticipated future developments and increased traffic due to a recent Bristol Hospital project.
The report also includes a list of necessary short-term improvements. These include securing access covers, replacing pedestrian push buttons and signage, applying sealant, replacing a malfunctioning pedestrian signal head, trimming vegetation to improve sight lines, and replacing a damaged controller unit. The Department of Public Works will be requesting funding this year to address these recommended improvements. Armed with information gained through the signal retiming project, City staff and leadership can plan future investments and improvements that will undoubtedly benefit residents and visitors to the city for years to come.
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