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As marijuana becomes legal in more states, it’s no surprise that people are taking part. In fact, General Motors is considering changing its testing policies to exclude marijuana. However, the Insurance Institute for Highway Safety (IIHS) claims that states with legalized recreational use of cannabis see an increase in crashes. 

A driver holding a joint | Getty Images

A new IIHS study suggests that crash rates are increasing in states that have legalized marijuana. Crash rates spiked with the legalization of recreational marijuana use and retail sales in Washington, Oregon, Nevada, Colorado, and California. Studies by the affiliated Highway Loss Data Institute (HDLI) suggest the same information. 

IIHS-HLDI president David Harkey explained that their latest research makes it clear that legalizing marijuana for recreational use does increase overall crash rates. It’s something that policymakers and safety professionals will need to address as more states move toward legalization. However, the way marijuana affects crash risk for individual drivers remains uncertain. 

How did they perform their study? 

To better understand the net impact on driver safety, researchers from IIHS and HLDI have conducted a series of studies since 2014 to examine how legalization affected crash rates and insurance claims in those that legalized recreational use. 

The most recent studies show that injury and fatal crash rates in Washington, Oregon, Nevada, Colorado, and California increased in the months following the relaxation of marijuana laws in each state. The retail sales in these five states correlate with a six percent increase in injury crash rates and a four percent increase in fatal crash rates compared to other states where the recreational use of marijuana remains illegal. 

This rise is consistent with the 2018 IIHS study of crashes reported by the police. Most of these didn’t involve injuries or fatalities. However, with the legalization of retail sales in Colorado, Oregon, and Washington, crash rates rose by five percent compared to neighboring control states. 

Insurance records show a similar increase in claims under collision coverage that pays for at-fault damage for an insured driver’s vehicle. In states with legalized marijuana, that was a four percent increase in collision claim frequency. 

Does marijuana make driving more dangerous? 

a scientist holding marijuana
Legalized Marijuana | Getty images

Maybe. Studies to determine if marijuana makes drivers more likely to crash have been inconsistent. When the IIHS collected data from injured drivers in emergency rooms in Denver, Colorado, Portland, Oregon, and Sacramento, California, showed no crash risk increase associated with any drug except when combined with alcohol. 

When interviewing and drug testing over 1,200 patients, four percent of drivers involved in crashes self-reported marijuana use compared to nine percent of patients that weren’t involved in accidents. Also, 13 percent of the crash-involved drivers tested positive for marijuana use only compared to 16 percent of the control set. 

But other factors may have led to increased crash rates. Colorado was the first state to legalize recreational marijuana and had a more significant spike in crash rates. But legalization led to a massive increase in tourism, leading to more drivers on the road. More studies need to be performed about how marijuana affects drivers to determine its risks.


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