Legal pot and car crashes: Yes, there's a link

Does driving while high have any impact on auto accident rates? Legalized recreational marijuana use in Colorado, Oregon and Washington correlates to about a 3 percent increase in auto collision claim frequencies compared to states without such legislation, according to a new Highway Loss Data Institute (HLDI) study. It's the first one the group has conducted since the drug went on sale legally.

"More drivers admit to using marijuana, and it is showing up more frequently among people involved in crashes," the study said.

The HLDI is affiliated with the Insurance Institute for Highway Safety, a nonprofit research organization that usually focuses on figuring out which cars are safest. The group is funded by auto insurance companies, which have a vested interest in not having to pay claims and -- of course -- hold a bias against impaired driving of any kind.

According to the HLDI, past researchers haven't been able to "definitively connect marijuana use with real-world crashes," and even a federal study failed to find such a link. "Studies on the effects of legalizing marijuana for medical use have also been inconclusive," said the HLDI.

Instead, the group focused on three states -- Colorado, where legal marijuana retail sales started in 2014, as well as Oregon and Washington, where sales began in 2015 -- and compared them to the collision claims in neighboring states such as Nevada and Utah, parts of which now allow only medical marijuana. It also factored in statistics regarding the three states where recreational use is now legal from before it became available to the general public.

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Source: Highway Loss Data Institute

Colorado saw the largest estimated increase in claim frequency -- 14 percent more than its bordering states, while Washington state was 6 percent greater and Oregon had a 4 percent increase. Allowing for the total control group, "the combined effect for the three states was a smaller, but still significant at 3 percent," said HLDI Vice President Matt Moore.

The group used collision claims because they are the most frequent kind insurers receive. Drivers file these claims for damage to their vehicle in a crash with an object or with another vehicle, generally when the driver is at fault, the HLDI said.

The HLDI said it's preparing for more of these studies and has already begun a "large-scale case-control study" in Oregon to find out if usage could be causing automotive injuries.

But the auto insurance industry's position on legalized marijuana is already crystal clear. "Worries that legalized marijuana is increasing crash rates aren't misplaced," said David Zuby, chief research officer of the Insurance Institute for Highway Safety. "The HLDI's findings on the early experience in Colorado, Oregon and Washington should give other states eyeing legalization pause."

  • Ed Leefeldt

    Ed Leefeldt is an award-winning investigative and business journalist who has worked for Reuters, Bloomberg and Dow Jones, and contributed to the Wall Street Journal and the New York Times. He is also the author of The Woman Who Rode the Wind, a novel about early flight.