Connecticut this week became the latest state to legalize recreational use of marijuana, and more are expected to follow.
The increased marijuana use that accompanies legalization has raised concerns about road safety.
Researchers at Insurance Institute for Highway Safety (IIHS) and the Highway Loss Data Institute (HLDI) since 2014 have been examining how legalization has affected crash rates and insurance claims, and evidence is emerging that crash rates go up when states legalize recreational use and retail sales of marijuana.
The most recent of these studies, released on June 17 by the IIHS, shows that injury and fatal crash rates in California, Colorado, Nevada, Oregon, and Washington jumped in the months following relaxation of marijuana laws in each state. The five states experienced a 6 percent increase in injury crash rates and a 4 percent increase in fatal crash rates, compared with other Western states where recreational marijuana use was illegal during the study period.
Only the increase in injury crash rates was statistically significant.
“Our latest research makes it clear that legalizing marijuana for recreational use does increase overall crash rates,” says IIHS-HLDI President David Harkey. “That’s obviously something policymakers and safety professionals will need to address as more states move to liberalize their laws — even if the way marijuana affects crash risk for individual drivers remains uncertain.”
Insurance records show a similar increase in claims under collision coverage, which pays for damage to an at-fault, insured driver’s own vehicle, according to HLDI’s latest analysis. The legalization of retail sales in Colorado, Nevada, Oregon, and Washington was associated with a 4 percent increase in collision claim frequency compared with the other Western states from 2012 to 2019. That’s down slightly from the 6 percent increase HLDI identified in a previous study, which covered 2012 to 2018.
While the evidence that crash rates have increased in states that legalized marijuana is mounting, it appears that further study is needed to determine whether marijuana use alone is responsible. Preliminary data suggests people who use alcohol and marijuana together are accountable for most of the crashes.
Another factor may be that marijuana users in counties that do not allow retail sales are driving to counties that do. The increased travel could lead to more crashes, even if their crash risk per mile traveled is no higher than that of other drivers.