Objective: To determine the safety effect of red light camera (RLC) programs, this study attempted to estimate its impact on collisions within Miami-Dade County, Florida Methods: A before-after evaluation using a comparison group along with traffic control correction was employed. Twenty signalized intersections with RLCs that began enforcement on January 1, 2011, were matched to 2 comparison sites located at least 2 miles from camera sites to minimize spillover effect. An empirical Bayes analysis was used to account for potential regression to the mean effects. An index of effectiveness along with 95% confidence intervals were calculated based on the comparison between the estimated and actual number of crashes in the after period.
Results: During the first year, RLC sites experienced a marginal decrease in right angle/turn collisions (-3%), a significant increase in rear-end collisions (+40%), and significant decreases in all injury (-19%) and RLR-related injury collisions (-24%). An increase in right angle/turning (+14%) and rear-end (+51%) collisions at the RLC sites was observed after 2 years despite camera enforcement. A significant reduction in RLR-related injury crashes (-17%), however, was still observed after 2 years. A nonsignificant decline in all injury collisions (-12%) was also noted.
Conclusions: RLCs showed a benefit in reducing RLR-related injury collisions at camera sites after enforcement commenced, yet its tradeoff was a large increase in rear-end collisions. There was inconclusive evidence whether RLCs affected right angle/turning and all injury collisions. Statutory changes in crash reporting during the second year of camera enforcement affected the incidence of right angle and rear-end collisions; nevertheless, a "novelty effect" could not be ruled out. Future research should consider events such as low frequencies of severe injury/fatal collisions and changes in crash reporting requirements when conducting RLC analyses.
Keywords: cameras; crashes; empirical Bayes; injuries; vehicle.