Analysis: State-Legal Cannabis Not Correlated with Increased Traffic Fatalities

Changes in the state-legal status of cannabis are not associated with rising motor vehicle fatalities, according to an analysis by the news agency Quartz Media LLC.

Researchers affiliated with Quartz Advisors assessed trends in fatal motor vehicle accidents in four legalization states – California, Maine, Massachusetts, and Nevada – as compared to five control states: Idaho, Indiana, Kansas, Nebraska, and Wyoming. Researchers analyzed data from 2016 to 2019. They excluded data from 2020 and 2021, which they determined to be “anomalous,” because the US as a whole experienced a 19 percent spike in traffic safety deaths during those years.

In the four legal states assessed, traffic deaths fell by an average of 12 percent in the three years immediately following the adoption adult-use marijuana legalization. By contrast, deaths increased nearly two percent over this same time in the five control states. Nationwide, traffic fatalities decreased 10.6 percent between 2016 and 2019.

“Traffic fatality rates did not increase in any of the four states that legalized in 2016 during that three-year period,” their analysis reported. “Three of the four states saw a significant decrease in vehicle deaths over that span, while the rate in Maine showed no change. Massachusetts saw the biggest drop, as rates fell 28.6 percent in the three years following legalization.”

It concluded: “There are legitimate concerns around the marijuana legalization debate. … However, based on our research and the research of others, the effect that legal marijuana could have on traffic safety should not be one of those concerns.”

Several prior studies have assessed whether the enactment of adult-use legalization is associated with an increased risk in the likelihood of motor vehicle accidents. The findings of those studies have yielded inconsistent results, with some studies identifying a minor uptick in crash rates in specific states several years following legalization and others finding no such change.

Data provided in 2021 by the Insurance Institute for Highway Safety identified a wide disparity in traffic safety trends among adult-use legalization states following state-level changes in law, with some jurisdictions experiencing an uptick in motor vehicle accidents and others experiencing a significant decrease. This disparity in outcomes indicates that changes in the marijuana policy alone are not consistent predictors of traffic safety trends.

Full text of the analysis, “Legalizing Marijuana Hasn’t Made Roads Less Safe,” is available from Quartz Advisors. Additional information on cannabis, psychomotor performance, and accident risk is available from the NORML Fact Sheet, “Marijuana and Psychomotor Performance.”