Proactive signal timing review & optimization

Proactive signal timing review and optimization uses actual traffic performance data to operate and manage traffic signals. This strategy can help improve safety, reduce vehicle delays, and help more finely target maintenance activities.

Key characteristics




WSDOT regions

Strategy description

With proactive signal timing review and optimization, engineers and maintenance technicians review local and coordinated intersection timings regularly and make timing changes to match current conditions better. Signal operators check on the health of the detectors, how well the green light time serves the movements that need it, and how well the signal coordination is operating. Signal operators rely on data and reports from the signal system to analyze how well the signal timing is serving the vehicle, bicycle, and pedestrian needs.

In some cases, signal operators and maintenance technicians receive reports from the signal system that highlights a variety of performance metrics to illustrate how well the intersection or group of intersections is operating. These performance metrics enhance the signal operators understanding of intersection or corridor performance issues, and are known as Automated Traffic Signal Performance Measures (ATSPMs).

A small sample of ATSPMs include:

  • Split monitor - Shows whether a movement is using all of the green time or not. If all of the green time is being used, then the engineer may want to increase the green time to increase the number of vehicles served during one green phase.
  • Percent arrival on green - Shows the percentage of vehicles arriving at the intersection while the light is green, which measures how well the signal coordination works. The higher the percent of vehicles arriving on green the better because it represents fewer vehicles waiting at a red light.

By using ATSPMs, engineers receive a view of how well traffic signals are operating throughout the day. This allows for adjustments that best fit the long-term and short-term needs of an intersection.

Operators can also optimize individual signals as needed. Having performance data readily available allows them to troubleshoot traffic signal issues reported by the public, such as green time that is too short, or a failed detector. Without ATSPMs in place, signal operators have to respond to complaints from the public with little to no data to understand what triggered the complaint.

Signal operators can review what happened at a traffic signal for any prior point in time, find the issues, and make changes to correct problems. Most of the time, operators can adjust signals without having to go to the location.

When to use this strategy

Proactive signal timing review and optimization and ATSPMs makes sense for:

  • Any traffic signal (urban or rural) Traffic signals that communicate back to a central server
  • Communications equipment can include anything from a low-speed dial-up phone line to a high-speed Ethernet connection

Strategy benefits:

  • Reduces collisions because the signal timing separates vehicle movements
  • Reduces the amount of time waiting at a red light
  • Reduces travel times because signal coordination can be fine-tuned based on the actual corridor or intersection performance
  • Failed traffic detection can be identified and repaired more quickly, and green time can be adjusted to better match the intersection needs
  • Assists in the planning, budgeting, design, or implementation of intersection enhancements

What you need in order to implement

Planning needs:

  • Before any signal optimization activities, the agency needs to understand the operating objectives for the corridor or intersection. For example, reducing travel times for vehicles on the primary route will be a different type of optimization than reducing pedestrian wait time.
  • Decide which automated signal performances will show whether the operating objectives are being achieved
  • Decide which automated signal performances should be measured because many have unique field equipment requirements to collect the data

Equipment needs:

  • Vehicle sensors that measure the traffic conditions, and detect pedestrians, bicyclists, buses, and emergency vehicles. Note: some ATSPMs do not require any sensors, but most do.
  • Intersection traffic signal controller that collects high-resolution data. High-resolution data includes the condition of every input and output at the intersection every 1/10 of a second.
  • Communications equipment between each intersection so the traffic signals can share the data with the central ATSPM application. The communications equipment can include anything from a low-speed dial-up phone line to a high-speed Ethernet connection.
  • Central ATSPM application that gathers the high-resolution data and turns it into performance measures

Maintenance needs:

  • ATSPMs provide real-time notifications that inform maintenance personnel if a piece of the traffic signal or detection equipment is faulty. The ATSPM report can be reviewed daily to proactively determine which maintenance activities to prioritize.

Agency resources needs:

  • ATSPMs require human interaction to resolve traffic issues for the traveling public. Therefore, agencies must provide the personnel resources to actively review the performance measures and be able to respond by repairing faulty equipment and/or making traffic signal timing changes.

Learn more about this strategy

Federal Highways Administration (FHWA), Every Day Counts Initiative, Automating Traffic Signal Performance Measures.

Federal Highways Administration (FHWA), Automated Traffic Signal Performance Measures.

Performance Measures for Traffic Signals, An Outcome-Oriented Approach (Fee).

National Operations Center of Excellence, Information from 2016 Automated Traffic Signal Performance Measures Workshop. 

About key characteristics

Location notes:

Proactive signal timing review and optimization is appropriate for any traffic signal (urban or rural).

Cost notes:

This strategy is one of the most cost-effective ways to manage and operate traffic signals with actual performance data. The most significant cost is the intersection sensors that are needed to collect the information and the personnel costs to analyze data and make adjustments or repairs.

Technology notes:

This strategy relies on data collected from sensors at the traffic signal. While this strategy can be used at traffic signals that don’t have intersection sensors and have only low-speed communications to a central location, it benefits from having multiple intersection sensors and high-speed communications. Multiple intersection sensors can produce more traffic signal performance information and high-speed communications enable traffic signal operators and technicians to respond faster.

Collaboration notes:

No collaboration is required to implement proactive signal timing review and optimization. However, if the operating agency wants to include transit vehicle performance information, then it requires collaboration with the transit agency.