Evaluating the effectiveness of freeway speed cameras: Evidence from a natural experiment in Dayton, Ohio

Nearly 42,000 people die annually in the United States in automobile crashes. Speed cameras are seen as an indispensable tool to prevent crashes and fatalities, while opponents merely see them as a means to generate revenue. Empirical evidence on the effectiveness of speed cameras in reducing automobile crashes is mixed primarily due to the endogeneity of the timing of camera activation and/or their placement. We circumvent these concerns by leveraging multiple plausibly exogenous state-level court cases and political infighting that turn freeway speed cameras off, on, and off again in Dayton, Ohio. We estimate the efficacy of cameras using a difference-in-differences estimator using untreated interstates and highways as controls. After a considerable number of tests across different samples, we find no significant evidence of a relationship between the use of freeway speed cameras and various measures of crashes.