Safety Impacts of Photo-Red Enforcement at Suburban Signalized Intersections: An Empirical Bayes Approach

Abstract

Photo-red enforcement entails cameras that photograph a vehicle entering an intersection after the traffic signal has turned red; a citation is then mailed to the vehicle's owner. Such a program was operated at 13 signals in Fairfax County, Virginia, between 2000 and 2005. This paper reports how photo-red enforcement affected crash frequency at the intersections. An empirical Bayes approach was used to detect the impact of the program on crashes while main-line traffic volume, yellow time, truck percentage, number of left-turning lanes, and speed limit were controlled. Cameras were definitely correlated with decreased red light running crashes (11% to 55%), increased rear-end crashes (32% to 85%), increased total crashes (0% to 23%), and decreased red light running injury crashes (5% to 64%). Cameras were probably associated with increased total injury crashes (5% drop to a 33% raise). These results are consistent with those of other studies with one notable exception: In the case of Fairfax County, the m...