Road traffic crash injuries near mobile speed cameras: a controlled before and after study

Speed cameras have been used in many countries as a traffic enforcement intervention to deter speeding and prevent road traffic crashes. Most of the research on effectiveness has been carried out at static speed camera sites and there is relatively little evidence about mobile cameras. Various methods have been used to evaluate local effectiveness of cameras. The appropriateness of those methods has not been assessed. Our study compares methods for investigating the local effectiveness of mobile speed cameras, using circles and lines methods for defining the local area of exposure, at various distances or radiuses from camera sites, and within strata of time after camera deployment, time of day, posted speed limit, and type of road user injured. It compares observed and expected numbers of personal injury crashes in the period 1996−2000, adjusted for seasonal and annual variation, after cameras were first deployed at 101 sites in South Wales and at 101 control sites matched for crash history, posted speed limit, and road class. We repeated the analysis using circle radiuses and line lengths of 0−100, 100−300, 300−500 an