Effects of Dynamically Activated Emergency Vehicle Warning Sign on Driver Behavior at Urban Intersections

Abstract

Emergency vehicles are subjected to substantial risks when traveling through urban signalized intersections, particularly when the cross street traffic is provided with a green signal indication. Much of this risk is due to a lack of awareness of the approaching emergency vehicles on the part of the cross street traffic. To mitigate this problem, a dynamically activated emergency vehicle alert system was developed to provide an additional visual cue to motorists of an impending emergency vehicle's approach. The alert system consists of an LED case sign, mounted near the curb line adjacent to a traffic signal, which displays an emergency vehicle symbol when activated by a transmitter installed in the emergency vehicle as it approaches an intersection. A before-and-after evaluation of these warning signs was conducted at five test intersections in two suburban communities near Detroit, Michigan. The results showed that the alert system significantly improved driver awareness and behavior at all study locations as determined by comparing various measures of effectiveness. Overall, the proportion of drivers who yielded the right-of-way to an approaching emergency vehicle increased from 77.1% before installation of the warning signs to 96.6% after installation. Drivers also tended to yield sooner when the alert system was in use, and when violations of the emergency vehicle right-of-way did occur, they generally happened sooner.