EFFECT OF CLEARANCE INTERVAL TIMING ON TRAFFIC FLOW AND CRASHES AT SIGNALIZED INTERSECTIONS

The timing of traffic signal clearance intervals (yellow and all-red phases) can affect accident rates at signalized intersections. When clearance intervals are not properly timed some drivers may be forced to choose between abruptly stopping or losing the cross-street red-light protection while crossing the intersection. Abrupt stopping can cause rear-end crashes, and the loss of cross-street red-light protection can cause right-angle crashes. Although driver response to yellow onset has been extensively researched, the effect on the rate of intersection crashes caused by departures from the recommended signal timing practice has not been systematically assessed. This article presents the highlights of a more extensive examination of this relationship.