Are mobile speed cameras effective?
OBJECTIVE: To identify the most appropriate metric to determine the effectiveness of mobile speed cameras in reducing road traffic related injuries. DESIGN: Controlled before and after study which compares two methods for examining the local effectiveness of mobile speed cameras-a circular zone around the camera and a route based method to define exposure at various distances from sites. SETTING: South Wales, UK. SUBJECTS: Persons injured by road traffic before and after intervention. INTERVENTION: Use of mobile speed cameras at 101 sites. MAIN OUTCOME MEASURES: Rate ratio of injurious crashes at intervention and control sites. FINDINGS: Camera sites had lower than expected numbers of injurious crashes up to 300 meters using circles and up to 500 meters using routes. Routes methods indicated a larger effect than the circles method except in the 100 meters nearest sites. A 500 meter route method was used to investigate the effect within strata of time after intervention, time of day, sp
