Transportation - Signal Timing Report

A project to have Salt Lake City’s signal timing plans reviewed and updated by out-of-area experts who have never worked on the Commuterlink system, was funded by the Energy Efficiency and Conservation Block Grant approximately one year ago. The intent of the project was to have a “fresh set of eyes” evaluate the City’s traffic signal timing software and philosophy, as well as improve the timing of the City’s traffic signals. Project goals included, determining how to immediately reduce traffic delays, fuel consumption and greenhouse gas emissions and, over the long term, determine how to improve the capability and efficiency of the signal control system.

 
The project consultant, KOA Associates, developed optimized traffic signal timing plans for weekday morning, midday, afternoon peak periods, weekend peak, and weekend off-peak periods. The updated timing plans have been implemented, tested and reviewed. Before and after travel time and stop data were compared. The consultant’s final report detailing the reduced traffic delay, fuel savings, and emissions achieved from the timing plan changes has been posted on the City’s website at:
 
 

Key Findings from the Report

The updated traffic signal timing plans:
  • save users 337,000 gallons of fuel annually
  • reduce delay 14% during the morning peak, 10% during the midday period, and 8% during the p.m. peak
This signal retiming effort reduces:
  • CO emissions 50,700 pounds annually
  • NOx emissions 10,000 pounds annually
  • VOC emissions 13,200 pounds annually
Salt Lake City’s traffic signal timing plan strategies and philosophies are sound and in line with national transportation industry standards. The City’s traffic signal control staff needs to be increased to allow signal retiming on a three-year basis. This is necessary because the efficiency of traffic signal timing plans degrade over time as traffic patterns evolve, thus requiring regular updating.
 
Salt Lake City’s timing plan performance is comparable to other cities with similar traffic signal networks.
 
Salt Lake City and its Commuterlink partners have used the current central traffic management software for 12 years. In the near future this software will no longer be supported by the manufacturer and will need to be replaced.