Red Light Violations and Crashes at Urban Intersections

High approach speeds coupled with aggressive driving often lead to the running of red lights at intersections. When motorists see a yellow light as they approach an intersection, they are supposed to stop unless such sudden stopping is unsafe. Entering an intersection during the red signal is a citable offense, and several states are working to legalize video detection and enforcement using red light violation camera systems. Such enforcement is targeted toward driver behavioral modification; in the absence of an all-red interval the motorist who enters an intersection during the red signal runs an extremely high risk of being struck by cross-street traffic. A study was performed in the city of Detroit, Michigan, to compare the red light violation characteristics of intersections with properly designed all-red intervals and those intersections without all-red intervals. In the absence of before violation data, a comparative parallel experimental study was used. It was hypothesized that providing an all-red interval following a yellow change interval would reduce right-angle crashes. A before-and-after crash analysis was performed at the all-red-interval treatment sites (sites that targeted a reduction of right-angle and injury crashes). The analysis indicated significantly lower red light violations at the treatment sites. The analysis also indicated an extraordinary reduction in right-angle and injury crashes. This study demonstrated that substantial benefits, in terms of reducing red light violations and right-angle crashes, can be achieved by introducing a well-designed all-red interval.