Benefits of Retiming Traffic Signals, The

Institute of Transportation Engineers. ITE Journal,  Apr 2004  by Sunkari, Srinivasa

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WHAT ARE THE BENEFITS OF RETIMING TRAFFIC SIGNALS?

Signal retiming has significant benefits for the traveling public. One of the direct benefits is the reduced delay experienced by motorists. Delay savings are more apparent for motorists traveling along coordinated signalized arterials. Motorists experience fewer stops and reduced fuel consumption.

Apart from the direct benefits, there also is a general public perception of reduced delay during travel. A side benefit may be reduced motorist frustration and improved safety.

Improving signal timing also has other indirect benefits. Reduced fuel consumption reduces emissions and, hence, improves air quality. Efficient signal timing also minimizes diversion of traffic to local and residential neighborhoods, potentially improving safety and traffic conditions in those areas. Improved traffic flow also reduces pavement wear and tear, minimizing the maintenance requirements of the public works department.

Finally, signal retiming efforts are opportunities for operating agencies to conduct quality control checks on controller settings for pedestrian, preemption and priority requirements.

Figure 1 gives a good illustration of the savings in user costs if traffic signals are retimed. The figure demonstrates that retiming traffic signals at periodic intervals provides significant savings in user costs in the form of reduced delays, stops, fuel consumption and other measures of effectiveness.

EXAMPLES OF SUCCESSFUL RETIMING PROJECTS

* Since summer 2002, the Maryland DOT has retimed about 215 signals in the Washington, DC, USA, suburbs and an additional 30 signals on the Route 650 (New Hampshire Avenue) corridor between Montgomery County, MD, USA and the District of Columbia. An analysis has shown that delays on these roads shrunk by about 13 percent and vehicles made 10 percent fewer stops at red lights. Fuel consumption also dropped by about 2 percent.

* Adjusting signal timing in Lexington, KY, USA, by responding to real-time traffic data reduced stop-and-go traffic delays by about 40 percent and accidents by 31 percent.

* According to the Institute of Transportation Engineers (ITE), traffic signal improvements reduce travel time by 8 to 25 percent. The reduction in travel time also reduces fuel consumption and emissions.

* The Fuel Efficient Traffic Signal Management Program in California demonstrated a benefit to cost ratio of 58:1. The program retimed 3,172 signals, resulting in 15-percent savings in delays, 8.6-percent savings in fuel consumption, 16-percent savings in stops and 7.2-percent savings in travel time (1988).

* The Traffic Light Synchronization (TLS) Program in Texas showed a benefit to cost ratio of 62:1. By retiming traffic signals with the TLS program, Abilene, TX, experienced reductions of 14 percent in travel time and 37 percent in delays. Overall, the program resulted in a 24.6-percent reduction in delays, a 9.1-percent reduction in fuel consumption and a 14.2-percent reduction in stops (1992).

* In Kitchener-Waterloo, Canada, 89 intersections that included arterials in commuter and commercial routes and central business district areas were retimed. The project demonstrated savings of 10 percent in travel time, 27 percent in delays and 20 percent in stops (1996).