Two new studies report that crashes are up by as much as 6 percent in the first states to legalize marijuana—Colorado Nevada, Oregon and Washington—compared with neighboring states that haven’t legalized marijuana for recreational use. The research from the Insurance Institute for Highway Safety (IIHS) and Highway Loss Data Institute (HLDI) come as campaigns to decriminalize marijuana gain traction with voters and legislators in the U.S., and Canada begins allowing recreational use of marijuana.
In one study, HLDI analysts estimate that the frequency of collision claims per insured vehicle year rose a combined 6 percent following the start of retail sales of recreational marijuana in Colorado, Nevada, Oregon and Washington, compared with the control states of Idaho, Montana, Utah and Wyoming. The combined-state analysis is based on collision loss data from January 2012 through October 2017.
A separate IIHS study examined 2012–16 police-reported crashes before and after retail sales began in Colorado, Oregon and Washington. IIHS estimates that the three states combined saw a 5.2 percent increase in the rate of crashes per million vehicle registrations, compared with neighboring states that didn’t legalize marijuana sales.
The 5.2 percent increase in police-reported crash rates following legalization of recreational marijuana use is consistent with the 6 percent increase in insurance claim rates estimated by HLDI.
“The new IIHS-HLDI research on marijuana and crashes indicates that legalizing marijuana for all uses is having a negative impact on the safety of our roads,” says IIHS-HLDI President David Harkey. “States exploring legalizing marijuana should consider this effect on highway safety.”
The two new studies were presented at the Combating Alcohol- and Drug-Impaired Driving summit, hosted by IIHS and HLDI at the Vehicle Research Center. The summit brings together highway safety and law enforcement experts to discuss the prevalence and associated risk of alcohol- and drug-impaired driving, as well as strategies to combat impaired driving.
