Last week, two studies on highway safety after cannabis legalization purported different findings and both drew headlines – one claimed accident rates were 3 percent higher in legal states than they would have been without legalization, while another found no increase, the Washington Post reports.
The Insurance Institute for Highway Safety study analyzed insurance claims for collisions between January 2012 and October 2016 in Colorado, Washington, and Oregon. In that study, researchers concluded that after adult-use sales began in Colorado, the state experienced a 14 percent higher collision claim rate than nearby Nebraska, Utah, and Wyoming. In Washington, rates were 6 percent higher than Montana and Idaho; and in Oregon, the rates were 4 percent higher than Idaho, Nevada, and Montana.
However, researchers at the University of Texas-Austin published a paper in the American Journal of Public Health which studied federal data on fatal vehicle crashes from 2009 to 2015 and concluded there was “no significant association between recreational marijuana legalization in Washington and Colorado and subsequent changes in motor vehicle crash fatality rates in the first 3 years after recreational marijuana legalization.”
According to the Post, while the two studies are aimed at the same target, they are measuring different things. The IIHS study is focused on all collisions, while the AJPH study is interested in fatal crashes.