New Study Suggests Marijuana's Impact on Crash Risk Has Been Exaggerated

Driving after toking is not safe, but it's not as dangerous as prohibitionists claim.


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Last week a Massachusetts legislative committee considering the prospect of marijuana legalization in that state noted that "there is no well-accepted standard for determining driver impairment from marijuana intoxication." It nevertheless recommended creating a legal standard for driving under the influence based on THC blood levels. Politicians are so worried about stoned driving that they are endorsing solutions they concede have no scientific basis. As I explain in my latest Forbes column, a new study suggests the fear underlying such proposals is overblown:

Pot prohibitionists frequently warn that legalization will flood the roads with dangerously stoned drivers, leading to a surge in traffic fatalities. So far there is not much evidence of such a surge in Colorado or Washington, where marijuana was legalized in 2012. A new study may help explain why: It looks like marijuana's impact on traffic safety has been greatly exaggerated.

Reporters and anti-pot activists commonly warn that marijuana use doubles the risk of a car crash. Even if that were true, toking would pale in comparison to drinking as a road hazard, since research indicates that a blood alcohol concentration of 0.10% quintuples the risk of an accident. But according to an analysis that's about to be published by the journal Addiction, the increase in crash risk associated with marijuana use is roughly 20% to 30%, as opposed to the widely cited estimate of 92%.

Read the whole thing.

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  1. Drugs cause people to be dangerous drivers, and marijuana is a drug, therefore marijuana causes people to be dangerous drivers.

    The logic is impenetrable.

    Seriously thought, about the worst thing pot does to drivers is cause them to drive slow and forget where they are going. It turns them into old people.

    1. *though*

    2. It turns them into old people.

      BAN IT.

    3. In my high school there was a kid who took a couple of marijuanas and then crashed his car. It was prom night and he killed his date and a bunch of other people.

      DRUGS KILL!!!

      1. He should have been more traditional.

        Drunk on alcohol

    4. Like using cell phones then.

  2. Driving is not safe. I probably wouldn’t want to be in the car with some novice not familiar with the effects, but I really have almost no concern about the danger of stoned drivers. Drunk people, people with kids in the car, people talking on the phone, people changing the radio, people who are a bit tired and people eating are all much more significant threats.

  3. I have ad blocker. The Forbes site doesn’t work for me. Way to go Jacob.

    1. Turn off your ad blocker on that page only. Forbes will thank you and won’t mention it again even though your software is blocking ads on every other page you visit. Of course its very likely that by 2017 this won’t work, but it is working now.

  4. “there is no well-accepted standard for determining driver impairment from marijuana intoxication.”


    Well, *maybe* how stupidly the driver crashed the car.

    1. Well that’s got me waxing nostalgic. What’s most remarkable to me is that almost 36 years later the arguments are still identical for all intents and purposes.

      The State of Colorado maintains a registry of residents authorized to use medicinal cannabis. As of 1/31/2016 there were 107,798 Colorado residents on that list. There has been a total of 320,229 residents who have had their names on that list.

      The State of Colorado also maintains a registry of residents authorized to operate motor vehicles. In addition to their names this registry includes the registrants past driving history. So how flippin’ hard would it be to compile a comparison of the average driver’s record to the average medicinal cannabis patient’s driving record?

      It still wouldn’t produce a valid reason to arrest people that have not and may never go out driving when impaired but it would go a long way to actually quantifying the “problem” of stoned drivers.

  5. A couple of interesting statistics were recently released. In 2015 reported sales of cannabis in Colorado came up $4 million short of $1 billion. That means the State collected $130-something million in gross tax revenue. Total gross revenue reported increased by just under 42.5%.

    For 2015 the Colorado State Patrol reports that rather than increasing by just under 42.5 percent, the total number of drivers arrested by the CSP for being cannabis addled and under the influence of another substance of impairment fell by 1.3 percent from 674 to 665. Drivers arrested solely for being cannabis addled also did not increase by just under 42.5 percent, but declined just under 2% from 354 to 347.

    The total number of DUI arrests made by the CSP was just under 22% higher in 2014 than in 2015. Total arrests declined by exactly 1000 from 5,546 in 2014 to 4,546 in 2015. Where did those 1000 drunk drivers go?

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