Caution: a comment on Alena Erke's red light for red-light cameras? A meta-analysis of the effects of red-light cameras on crashes.

In Red Light for Red-Light Cameras?, Alena Erke concludes that "... on the whole, redlight cameras do not seem to be a successful safety measure." Although Erke's survey of the literature appears to have been comprehensive, her review of the studies was not critical. She appears to have accepted the authors' descriptions of their analyses rather than providing readers with her own considered opinion of how valid those analyses were and what their true implications might be. For the meta-analysis leading to her final conclusion, Erke combines data from two questionable studies with three other "well-controlled" studies. Non-peer-reviewed studies received substantial statistical weight in the meta-analysis. These problems likely produce misleading results. If the highway safety field is to succeed in identifying for policymakers those strategies that are most likely to reduce the human tragedy of motor vehicle crashes, we need first to focus on conducting valid research and analysis. Adding precision to the estimated benefits of those strategies through meta-analysis is important, but secondary, and cannot replace the function of a systematic and critical review.