SAFETY ASPECTS OF USING VEHICLE HAZARD WARNING LIGHTS, VOLUME 1

The report describes a series of experiments that were conducted to examine the effectiveness of four-way flashers. Both the disabled vehicle situation and the slow-moving vehicle situation were examined at two- and four-lane locations under both daylight and nighttime conditions. The disabled vehicle tests involved parking a test vehicle (either a car or a tractor-trailer) at the side of the road and monitoring the behavior of drivers. The slow-moving vehicle tests involved introducing a staged slow-moving vehicle (either a car or a tractor-trailer) into the traffic stream and observing the overtaking vehicles. At the disabled vehicle, red and amber four-way flashers as well as flares, reflectorized triangles, headlights, and other situational factors were evaluated. For the slow-moving vehicle tests, the effects of red and amber flashers as well as a 30 and 40 mph (48.3 and 64.4 kph) slow-moving vehicle were examined.