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Effect of recreational marijuana sales on police-reported crashes in Colorado, Oregon, and Washington

Monfort, Samuel S.
Insurance Institute for Highway Safety
October 2018

In January 2014, Colorado became the first U.S. state to allow retail sales of recreational marijuana, with Washington (July 2014) and Oregon (October 2015) following shortly afterward. With more states weighing legalization, it is important to understand the degree to which recreational marijuana legalization has affected traffic safety outcomes. The current study was based on the 2018 Highway Loss Data Institute research on the subject, which estimated that the legalization of retail sales was associated with a 6.0% increase in insurance collision claims compared with control states. The current study investigated police-reported crashes rather than insurance claims. Crash rates were computed for each month between January 2012 and December 2016 for the three study states as well as their neighboring states, which served as controls. Controlling for several demographic factors, the change in crash rate that occurred after recreational marijuana was legalized was compared with the change in crash rate in the control states over the same time frame. The legalization of retail sales in Colorado, Washington, and Oregon was associated with a 5.2% higher rate of police-reported crashes compared with neighboring states that did not legalize retail sales. These results contribute to the growing body of research on the impact of recreational marijuana legalization.