Emergency vehicle signal priority pilot project near Houston, Texas found to have no detrimental effects on intersection operations and pleases emergency services personnel.

Harris County deployed emergency medical services priority signal system at 50 intersections on Louetta Road, one of the first deployments of its type in the United States.


NCHRP Synthesis 447: Active Traffic Management for Arterials

Summary Information

This synthesis documents the state of the practice associated with designing, implementing, and operating active traffic management (ATM) on arterials. Information for this synthesis was gathered through a literature review of advanced ATM methods for arterials and in-depth telephone interviews of agencies selected through a screening interview. The study has provided information on strategies used to actively manage traffic and congestion on arterials; situations and operating conditions in which ATM strategies have been successfully and unsuccessfully deployed on arterials; and system and technology requirements associated with implementing the strategies.

Project Introduction

Harris County initiated a pilot project to install an emergency medical services (EMS) priority signal system at 50 intersections in the Houston area (Spring, Texas). The pilot took place on Louetta Road, between State Highway 249 and Interstate 45. A module was placed inside the signal controller cabinet that monitors the signal phase and allows real-time preemption for EMS vehicles. Additionally, DMSs are mounted above each lane approaching an intersection indicating the direction and location of approaching emergency vehicles. Within the emergency vehicle is a module for tracking and transmitting vehicle data to the signal controller. This notifies the signal of an approaching emergency vehicle, allowing the signal to adjust the phase to allow the emergency vehicle to get through the signal on a green.

Prior to implementation, the agency needed to ensure the existing controllers could handle the components and software needed, which they could. The two primary technologies implemented were the components and software needed for the emergency priority system and a 2070 controller. Though Harris County was one of the first locations in the country to implement an EMS signal priority, so there were some initial technical challenges in getting the system to work as desired.


Emergency services personnel have been happy with the system, and the agency has not found it to be detrimental to normal intersection operations. Harris County plans to study the impacts on intersection LOS more thoroughly in the future. Overall, the system has been a success and Harris County has decided to continue expanding the original pilot study of 50 intersections to approximately 220 intersections in the northwest part of the county in the next 3 years.

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Deployment Locations