The Impact of Red Light Cameras (Automated Enforcement) on Safety in Arizona: Final Report

1010926621567892005Final ReportPDFTech ReportFHWA-AZ-05-550Final Report 550SPR-PL-1-(61) 550Automated enforcementCamerasCrash severityCrash typesBefore and after studiesImpact studiesLeft turn phaseRecommendationsRed light runningSafetySignalized intersectionsSpeedTraffic crashesTraffic law enforcementTraffic safetyTraffic signal timingWarning signsRed light enforcement cameraTraffic lightsTraffic signalsHighwaysOperations and Traffic ManagementResearchSafety and Human FactorsSecurity and EmergenciesI73: Traffic ControlI80: Accident StudiesUnited StatesArizonaPhoenix (Arizona)Arizona. Dept. of TransportationWashington, SimonShin, KangwonUniversity of ArizonaArizona. Dept. of TransportationUnited States. Federal Highway AdministrationSemmens, JohnUS Transportation CollectionRed Light Cameras (RLCs) have been used in a number of US cities to yield a demonstrable reduction in red light violations; however, evaluating their impact on safety (crashes) has been relatively more difficult. Accurately estimating the safety impacts of RLCs is challenging for several reasons. First, many safety related factors are uncontrolled and/or confounded during the periods of observation. Second, \u201cspillover\u201d effects caused by drivers reacting to non-RLC-equipped intersections and approaches can make the selection of comparison sites difficult. Third, sites selected for RLC installation may not be randomly selected, and as a result may suffer from the regression to the mean effect. Finally, crash severity needs to be considered to fully understand the safety impacts of RLCs. With these challenges in mind this study was designed to estimate the safety impacts of RLCs on traffic crashes at signalized intersections in the state of Arizona and to identify which factors are associated with successful installations. RLC equipped intersections in the cities of Phoenix and Scottsdale are examined in detail to draw conclusions as to the relative success of RLC programs in these two jurisdictions. Both jurisdictions are operating successful installations of RLCs. Factors related to RLC effectiveness appear to include crash type and severity, left-turn phasing, presence of warning signs, approach speeds, and signal timing. Recommendations are made as to under what conditions should RLCs be considered.74