Effects of Speed Cameras on Intersection Accidents: Evidence from Dayton

: Over 30,000 people die annually in automobile accidents in the United States, which equates to about 10 in every 100,000 deaths. Empirical evidence on the effectiveness of speed cameras is mixed primarily due to the endogeneity of the timing and placement of the cameras. I am able to circumvent these issues by leveraging multiple court cases and political infighting that turn the cameras off, on, and off again on two separate data sets. Using a before-after and a difference-in-differences estimator over a twenty-year period, I find all three exogenous shocks suggest roughly the same effect. Speed cameras are weakly effective at preventing the total number of monthly accidents (0.3), certain types of “Angle” accidents (0.15), and most importantly, the severity of those accidents (0.14), which equate to about an 18.5%, 20%, and 41% decrease respectively.