Legalizing recreational marijuana linked to increased car crashes, insurance study finds

After retail marijuana sales began in Colorado, the increase in collision claim frequency was 14% higher than in nearby Nebraska, Utah and Wyoming. (Photo: iStock)
A recent insurance study links increased auto crash claims to legalized recreational marijuana.

Legalizing recreational marijuana use in Colorado, Oregon and Washington has resulted in collision claim frequencies that are about 3% higher overall than would have been expected without legalization, a new Insurance Institute for Highway Safety (IIHS) Highway Loss Data Institute (HLDI) analysis shows.

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Colorado and Washington were the first states to legalize recreational marijuana for adults age 21 and older with voter approval in November 2012. Retail sales began in January 2014 in Colorado and in July 2014 in Washington. Oregon voters approved legalized recreational marijuana in November 2014, and sales started in October 2015.

“The combined-state analysis shows that the first three states to legalize recreational marijuana have experienced more crashes,” says Matt Moore, senior vice president of HLDI. “The individual state analyses suggest that the size of the effect varies by state.”

Colorado saw largest increase in claims

Colorado saw the biggest estimated increase in claim frequency compared with its control states. After retail marijuana sales began in Colorado, the increase in collision claim frequency was 14% higher than in nearby Nebraska, Utah and Wyoming. Washington’s estimated increase in claim frequency was 6% higher than in Montana and Idaho, and Oregon’s estimated increase in claim frequency was 4% higher than in Idaho, Montana and Nevada.

HLDI’s new analysis of real-world crashes provides one look at the emerging picture of what marijuana’s legalization will mean for highway safety as more states decriminalize its use. In the coming years, more research from HLDI and others will help sharpen the focus. As HLDI continues to examine insurance claims in states that allow recreational use of marijuana, IIHS has begun a large-scale case-control study in Oregon to assess how legalized marijuana use may be changing the risk of crashes with injuries. Preliminary results are expected in 2020.

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In addition to Colorado, Oregon and Washington, five other states and Washington, D.C., have legalized marijuana for all uses, and 21 states have comprehensive medical marijuana programs as of June. An additional 17 states permit limited access for medical use. Marijuana is still an illegal controlled substance under federal law.

“Worry that legalized marijuana is increasing crash rates isn’t misplaced,” says David Zuby, executive vice president and chief research officer of the IIHS. “HLDI’s findings on the early experience of Colorado, Oregon and Washington should give other states eyeing legalization pause.”

More about the analysis

HLDI conducted a combined analysis using neighboring states as additional controls to examine the collision claims experience of Colorado, Oregon and Washington before and after law changes. Control states included Idaho, Montana, Nevada, Utah and Wyoming, plus Colorado, Oregon and Washington prior to legalization of recreational use.

During the study period, Nevada and Montana permitted medical use of marijuana, Wyoming and Utah allowed only limited use for medical purposes, and Idaho didn’t permit any use. Oregon and Washington authorized medical marijuana use in 1998, and Colorado authorized it in 2000.

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HLDI also looked at loss results for each state individually compared with loss results for adjacent states without legalized recreational marijuana use prior to November 2016.

Data spanned collision claims filed between January 2012 and October 2016 for 1981 to 2017 model vehicles. Analysts controlled for differences in the rated driver population, insured vehicle fleet, the mix of urban versus rural exposure, unemployment, weather and seasonality.

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