IIHS Research Links Legalized Marijuana and Increased Collisions

One day after legal marijuana in Canada, the IIHS reports that collisions are up in the US states that have also legalized the drug. By as much as six percent.

The research is the result of a pair of studies by the IIHS and HLDI. That's the Insurance Institute for Highway Safety, the group best known for their crash testing, and the Highway Loss Data Institute, which supports the IIHS using studies of insurance data reporting.

"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 first study was an analysis of collision claims per insured vehicle in Colorado, Nevada, Oregan, and Washington from January 2012 through October 2017. The control states used were Idaho, Montana, Utah, and Wyoming.

The HLDI analysts looked at rated driver population, fleet of insured vehicles, urban and rural mix, weather, and other variables. Accounting for those, HLDI estimates that the frequency of collision claims rose six percent for the four states that legalized marijuana. Claim frequency is the number of claims per 100 insured vehicle year.

A second study looked at police-reported collisions from 2012-2016. Before and after retail sales of marijuana started in Colorado, Oregon, and Washington. The IIHS estimated that those three states saw an increase of 5.2 percent in the rate of crashes per million vehicle registrations compared with nearby states.

It's important to note, though, that the link between marijuana and collisions isn't as clear as the link between alcohol and crashes. The statistics were for an increase in collisions and claims of all types. The IIHS notes that states don't all include consistent information on drug use and that drug test procedures are inconsistent. More drivers are tested for alcohol than for drugs. Harkey says that "despite the difficulty of isolating the specific effects of marijuana impairment on crash risk, the evidence is growing that legalizing its use increases crashes."

Impairment is impairment, no matter what the substance that causes it. Police across Canada took to social media yesterday to remind drivers of that fact, and that it's not ok to toke and drive. Winnipeg Police have already issued at least one ticket for consuming while driving, for a hefty $672 fine. Ontario Provincial Police remind you that if you're transporting marijuana in your vehicle that it needs to be in the original sealed package or packed in baggage that is not "readily available" to anyone inside the vehicle. They're already issuing $215 fines for that offence.