Case studies of several transportation departments updating traffic signal systems estimated at least 10 percent reduction in delays, 23 percent reduction in the number of stops, and 3.5 percent reduction in fuel consumption as a result of signal system upgrades and retimings.
From the 2007 National Traffic Signal Operation Report Card Technical Report.
Made Public Date


United States


United States


United States


United States


United States

National Traffic Signal Report Card: Technical Report 2007

Summary Information

The 2007 Traffic Signal Self-Assessment, a voluntary self-assessment survey, was taken by 417 agencies in the US and Canada in 2006, in order to determine their "report card" grade for traffic signal operations. This report card uses a questionnaire to determine grades for management, individual signal operations, coordinated signal operations, signal timing practices, traffic monitoring and data collection, and maintenance. The self-assessment is one way for agencies to evaluate their existing practices and create a plan to improve their traffic signal operations and management. The 2007 National Traffic Signal Operation Report Card Technical Report synthesizes the results of that survey and provides some case study examples of improvements made by upgrades to signal timing and the benefits received by the travelers in their service areas.

Upgrading timing infrastructure and retiming corridors to provide improved traffic flow during peak hours in peak directions can result in significant reductions in delay, number of stops, fuel consumption, travel time and emissions. Case studies for Austin and Plano, Texas, Nashville, Tennessee, Naperville, Illinois and Alpharetta, Georgia show reductions in those five areas after evaluating and upgrading their traffic signals as a result of their performance on the 2005 Traffic Signal Self-Assessment. These improvements were highlighted in the 2007 National Traffic Signal Operations Report Card Technical Report.

Delay Reductions

  • Austin, TX saw reductions in travel delays of 2.3 million hours (almost 10 percent)
  • Plano, TX saw reductions of nearly 750,000 hours.
  • Nashville, TN saw 27 percent reductions.
  • Alpharetta, GA saw 31 percent reductions.

Stop Reductions

  • Austin saw reductions in stops by 195.1 million. Austin’s reduction in stops was a 28 percent drop.
  • Plano saw reductions of 36.1 million stops.
  • Alpharetta saw a 23 percent reduction in stops.

Fuel Reductions

  • Austin consumed 1.3 million less gallons of fuel
  • Plano reduced its fuel consumption by nearly 850,000 gallons.
  • Nashville saw nine percent reductions in fuel consumption.
  • Alpharetta saw eight percent reductions in fuel consumption.

Travel Time Reductions

  • Alpharetta estimates that updates to the signal systems reduced travel time by 17 percent.
  • Naperville, IL estimates travel time reductions of 31.8 percent.

Emissions Reductions

  • Naperville also estimates that the upgrades to their signal systems reduced emissions in their city by over 200 tons.
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