Identify a single agency to be responsible for maintenance of an emergency vehicle preemption system.
The experience of multiple agencies with emergency vehicle preemption systems.
Made Public Date


Fairfax County
United States


St. Paul
United States

Traffic Signal Preemption for Emergency Vehicles: A Cross-Cutting Study


Emergency vehicles operating in metropolitan areas with high congestion levels are at an increased risk for involvement in crashes and are subject to unpredictable delays in reaching the scene of a fire or crash. One way to offset the effects of congestion is the installation of emergency vehicle preemption (EVP) equipment at signalized intersections. This ITS technology provides a special green interval to the approach serving the emergency vehicle while providing a special red interval on conflicting approaches. Providing a green light at signalized intersections will reduce conflicts, driver confusion, and emergency response times.

In January 2006, the Federal Highway Administration produced a cross-cutting study to examine emergency preemption at signalized intersections in a number of communities across the United States. To show a wide range of deployment options, three jurisdictions – Fairfax County, Virginia; Plano, Texas; and St. Paul, Minnesota – were identified and officials were interviewed. The purpose of the study was two fold: to increase awareness among stakeholders – police, fire, rescue, and emergency medical services (EMS) – of the benefits and costs of EVP, as well as to reduce the time it takes to move from a plan to realizing improvements in the delivery of emergency services.

Lessons Learned

An Emergency Vehicle Preemption (EVP) system involves many different stakeholders who may not typically communicate except during major incidents. These stakeholders will include police, fire and rescue, emergency medical services (EMS), traffic engineering, and possibly transit agencies if transit priority is also being implemented. These agencies need to be involved in a formal and collaborative manner, communicating frequently, during EVP system planning and implementation. But once the system is deployed, it moves to the operations and maintenance phase, and communication between agencies may not be as frequent. Therefore, a clear method for reporting system problems and a well defined communication hierarchy among all the agencies involved are required to avoid delays in making any necessary adjustments or repairs.

The key to the successful maintenance of an EVP system is to identify a single agency to be responsible for scheduling, coordinating, and funding system maintenance. Maintenance can be handled by either the traffic engineering department or the fire/rescue and EMS departments. Many traffic engineering departments will want to maintain the equipment themselves in order to control access to traffic signal controller cabinets. Should the fire and rescue departments perform maintenance, either in house or by contract, it may be necessary to have a memorandum of agreement with the traffic engineering department to document important procedures, such as access to controller cabinets, service call precedence, service log requirements, and any other necessary site-specific coordination issues.

Based on the experiences of two jurisdictions, the following issues were identified to improve EVP system maintenance:

  • Develop a maintenance problem reporting channel. The purpose of a maintenance problem reporting channel is to enable the users of the system to easily report problems so that problems can be screened for response priority, minimizing the potential for dangerous situations. In Fairfax County, Virginia, the Virginia Department of Transportation (VDOT) provides a technician to oversee the maintenance of the EVP system even though system maintenance is contracted by the fire and rescue agency.
  • Ensure that a standard fault isolation protocol is in place. Having a documented process for trouble-shooting will reduce the repeat/recur rate as well as the false alarm rate for problems requiring maintenance.
  • Perform concurrent EVP system maintenance with traffic signal equipment maintenance. In addition to servicing maintenance calls, there may be benefit in performing preventive maintenance in conjunction with regular traffic signal equipment maintenance. A task such as detector lens condition inspection can be done in conjunction with signal lamp replacement. In St. Paul, Minnesota, they report that this practice has helped reduce the number of service calls.

This lesson indicates the value of effective maintenance programs to ensure that an EVP system continues to provide the highest degree of benefit after deployment. Identifying a single agency to be responsible for overall system maintenance and developing reporting procedures for all agencies to follow improves the overall maintenance of the system and provides the most benefit to the community. When EVP systems are implemented and maintained effectively, the negative impacts on traffic flow are not significant and public acceptance of the system is high. EVP systems are ITS solutions that help meet local and regional transportation goals to improve safety, mobility, and customer satisfaction.

Traffic Signal Preemption for Emergency Vehicles: A Cross-Cutting Study

Traffic Signal Preemption for Emergency Vehicles: A Cross-Cutting Study
Publication Sort Date
William C. Louisell, SAIC
Prepared by the FHWA USDOT

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