"Using population-based data from 1985 to 2014, we found that, first, states that enacted MMLs during the study period had lower fatality rates compared with states without MMLs. Second, on average, traffic fatalities further decreased in states post-MML, with both immediate (sudden change in fatality rate after MML enactment) and gradual (change in rate trend after MML enactment) declines over time in those aged 25 to 44 years. Third, the association between MML and traffic fatalities varied considerably across states. Fourth, the presence of operational dispensaries was also associated with reductions in traffic fatalities in those aged 25 to 44 years.
"We found that, on average during the study period, MML states had lower traffic fatality rates than non-MML states. It is possible that this is related to lower levels of alcohol-impaired driving behavior in MML states. Evidence from the Behavioral Risk Factor Surveillance Systems data from 200027 and 201228 shows that states that have enacted MMLs, compared with non-MML states, had, on average, lower proportions or rates of drivers endorsing having driven after having too much to drink. In addition, other unmeasured characteristics, including strength of public health laws related to driving, infrastructure characteristics (e.g., high-technology roads), or quality of health care systems, may partially explain these findings."


Julian Santaella-Tenorio, Christine M. Mauro, Melanie M. Wall, June H. Kim, Magdalena Cerdá, Katherine M. Keyes, Deborah S. Hasin, Sandro Galea, and Silvia S. Martins. US Traffic Fatalities, 1985–2014, and Their Relationship to Medical Marijuana Laws. American Journal of Public Health: February 2017, Vol. 107, No. 2, pp. 336-342.
doi: 10.2105/AJPH.2016.303577