EVP Optical Detectors in the MAG RegionMAG conducted a study about current Emergency Vehicle Preemption (EVP) practices in the MAG region. The findings of the study are organized into four sections:

  • Section 1, Regional EVP Inventory and Operational Challenges: Describes the state of EVP deployment in the MAG region and associated emergency response automatic or mutual aid operations issues.
  • Section 2, Review of EVP Technologies: Provides a review of current and emerging EVP technologies.
  • Section 3, Case Studies: Describes relevant practices around the nation that could benefit the MAG region.
  • Section 4, Future Considerations: Provides practices to improve the interoperability, consistency, and operational coordination across the MAG region.

EVP Emitter Installed on a City of Tempe Fire Engine

EVP is done by adjusting traffic signals. This starts with communications between a receiving device on a traffic signal and an emitter on an approaching emergency vehicle. The goal is to ensure the emergency vehicle’s safe passage through the intersection. Emergency vehicles with an emitter can request traffic signal preemption as they near an intersection. Several areas in the MAG region installed EVP systems after the technology was introduced in the early 1980s. With a goal of reducing response times, EVP capability is considered by first responders and transportation agencies an essential function of traffic signal operations.

While the Manual on Uniform Traffic Control Devices (MUTCD) specifies the standards for going into and out of preemption, there is a lack of guidance in the vital aspects of EVP operations. This includes preemption signal phase, confirmation light, data encryption, and needed inter-agency coordination to support emergency response automatic or mutual aid agreements. The distinction of inter-agency support is important. The Valley Wide Automatic Aid system involves a centralized dispatch by Phoenix Alarm. This results in the nearest emergency resource, regardless of agency and geographical boundaries, responding to the event. Mutual aid agreements are in place so agencies will support each other. This MAG EVP State of the Practice Study intends to address these knowledge gaps by identifying priority issues and recommending feasible approaches toward improved regional coordination.


Basic Components of the Optical-Based EVP System

Senior Program Manager - ITS and Safety
Sarath Joshua

About MAG

The Maricopa Association of Governments (MAG) is a Council of Governments (COG) that serves as the regional planning agency for the metropolitan Phoenix area.

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