Impacts of the San Diego Photo Red Light Enforcement System on Traffic Safety

The paper reports on the analysis of violation and crash data as part of an evaluation of the impact on traffic safety of the San Diego Photo Red Light Enforcement System. The system was found to have resulted in a statistically significant reduction in the number of red light running violations. The decreases in violations occurred at almost all camera enforced intersections and the decreases continued, at a diminishing rate, throughout the period the cameras were operated. The impact on traffic safety was more complex. For traffic traveling in the enforced direction at intersections with red light cameras, crashes attributable to red light running decreased after implementation to approximately 60 percent of pre-enforcement rates, while rear end crashes increased to approximately 140 percent of pre-implementation levels. These before-and-after changes in crash rates were statistically significant, while there were no significant changes in crash rates for traffic traveling in directions not covered by the red light cameras. In addition, it is concluded that photo enforcement was more effective in reducing crashes at intersections where through movement was enforced, than where left turns were enforced