Investigating the Effect on Driver Performance of Advanced Warning Flashers at Signalized Intersections

This report summarizes the findings of a human factors analysis to determine the effects of advanced warning flashers (AWFs) on simulated driving performance. The Minnesota Department of Transportation sponsored the project. Researchers used the flat-screen simulator at the University of Minnesota Human Factors Research Laboratory to conduct experiments. They measured vehicle speed, braking, and acceleration/deceleration during simulated driving and visually observed stopping behavior. In addition, they analyzed responses to a post-test questionnaire. They created a 11.3-mile simulated driving environment with 10 signalized intersections and configured four experimental models: low speed limit (SL) of 50 miles per hour with no AWFs, low SL with AWF at each intersection, high SL of 65 miles per hour with no AWFs, and high SL with AWF at each intersection Researchers set different vehicle-signal proximity intervals, with all green/no yellow as the control, and zero seconds with the vehicle adjacent to the signal, two seconds, three-and-a-half seconds, or five seconds. With each model, they assigned two intersections each proximity interval, with the sequence of intersection proximity intervals ordered differently for each model. Each of 24 subjects completed duplicate driving trials with each model. The study revealed that, relative to intersections with no AWFs, drivers who encountered yellow signals at AWFs intersections: stopped more frequently at low SLs but not at high SLs, drove more slowly while approaching intersections with two and three-and-a-half second proximity intervals, and displayed less inconsistent behavior at intersections with short proximity intervals. Researchers concluded that AWFs assist drivers with decision-making behavior and promote safer driving behavior. They recommended field research to study an actual environment.