Knowledge Resources

This report evaluated the emergency vehicle traffic signal preemption system deployed in the City of Houston between 1991 and 1992. The system was designed to activate or extend green time for emergency vehicles as they approached signalized intersections. Emitters were installed on emergency vehicles and then calibrated to activate signals within a quarter mile. The preemption system allowed cross street traffic to stop and clear each intersection normally. Traffic queues in approach lanes could then pull through and make way for emergency vehicles.

Field tests were run to measure travel time for emergency vehicles (without sirens activated) before and after installation at 22 intersections within two fire districts (11 per district). After a year of operations, the average emergency vehicle travel time decreased 16 percent in one district, and 23 percent in the other.