Fatal Car Crashes and Marijuana Legalization

An increasing number of states are legalizing recreational use of marijuana. There are concerns about its impact on road safety. This empirical study uses the experience from Michigan, California, and Colorado to test whether marijuana legalization has had any significant impact on cannabinoid-related fatal crashes. A Poisson difference-in-difference style estimation is applied in a panel data setting. MI, CA and CO are used as the treatment group, where recreational marijuana has been legalized. The control groups are the states of Ohio, Indiana and Texas, which did not have recreational marijuana legalized at the time. The treatment effect is found to be significant, thus legalization and retailing of marijuana have statistically significantly increased the number of cannabinoid-related and overall fatal crashes in the states that have legalized it in the period of study.