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Study Finds Alcohol 10 Times Deadlier Than Cannabis on the Road

November 17, 2017
Researchers who examined drug tests from drivers involved in more than 3,600 auto crashes have found that alcohol is about ten times more likely to cause a fatal crash than cannabis.

Drunk drivers were 17.8 more likely to cause a fatal crash than sober drivers. Cannabis-influenced drivers were 1.65 times more likely.

In a study published earlier this month in the journal PLOS-One, scientists at the University of Lyon looked at data from all fatal accidents that occurred in France during 2011. They estimated the heightened risk of driving under the influence of various substances and found that “drivers under the influence of alcohol are 17.8 times more likely to be responsible for a fatal accident,” when compared to completely sober drivers. Drivers under the influence of cannabis, by contrast, are 1.65 times more likely to be responsible for causing a fatal accident.

Those findings are in line with most recent studies of alcohol and cannabis and driving risk. Earlier this year David Bienenstock investigated the science behind drugged driving estimates, and found that THC-positive drivers have a 5% greater crash risk than drivers with no drugs or alcohol in their system. That figure came from the largest domestic case-control study to date, which was published by the National Highway Traffic Safety Administration, a federal agency. That same study found that drivers with a blood alcohol level of .08, the legal limit in most states, were 293% more likely to be involved in a crash. Texting drivers were 310% more likely to crash. 


Taking Drugged Driving Seriously: What Does the Science Say?

Past investigations “have shown a decreased capacity of drivers under the influence of cannabis, in particular a decrease in attention, increased reaction time and reduced ability to control direction,” the French researchers noted. Drivers under the influence of alcohol “tend to drive faster, which goes hand in hand with an over-estimation of their own capacities,” the researchers added, “whereas drivers under the influence of cannabis tend to drive more cautiously.”

For a deeper look at the most widely respected and cited studies on driving under the influence, check out David Bienenstock’s feature, “Taking Drugged Driving Seriously: What Does the Science Say?” published earlier this year by Leafly.

Bruce Barcott's Bio Image

Bruce Barcott

Leafly Senior Editor Bruce Barcott oversees news, investigations, and feature projects. He is a Guggenheim Fellow and author of Weed the People: The Future of Legal Marijuana in America.

View Bruce Barcott's articles

  • abie cee

    Unscientific “estimation” 1/10. Reality is 1/1,000,000.

    • Neuro

      Nice that you have the “real” figures. Those scientists and their ability to do actual math. By the way, please cite either of those 2 numbers from the article you read because I just can’t get the numbers to work that way, no matter how badly I mangle the math.

      • Jessy Ln

        I’ll try, the headline at the top “Study Finds Alcohol 10 Times More Deadly Than Cannabis on the Road” first set of numbers sober driver 1.00(100%) likelihood of causing a fatal crash, thc intoxication risk is times 1.65 (165%), alcohol intoxication risk is times 17.80 (1,780%). 1780/165 = 10.78. I dont think thats right. I’m guessing it more like 1680/65 = 25.84. But if someone who didn’t drop out of highschool wants to correct me that’d be great. The second set, this seems right to me, risk of being involved in a crash: thc intoxication 5% more likely , legal limit .08 alcohol intoxication 293% more likely. 293/5 = 58.60. 58.60>10, 25.84>10, 10.78>10. Are any of these right, fellow internet people?

        • joshuaj02

          comparing fatal weed crashes and fatal alcohol crashes
          therefore ratio between the two
          reduces to 1:10.78
          =10.78x more deadly alcohol crashes than deadly weed crashes.

          you are confused

  • Turner Kayston

    Now if only Canada would actually look at such science and evidence for the upcoming prohibition 2.0, but they actively choose not to.

    • Jessy Ln

      You have no respect for the people who inherited their wealth in the form of alcohol and pharma industry ownership. You’re talking about 100’s of people with virtually no marketable skills losing their means of luxury. despicable.

  • dcard88

    Most humans don’t have more fun or feel the need to go faster when high. Not the case with alcohol. I love to drive fast after a few beers although I haven’t since I have had children.

    • AZDiver

      That’s precisely the problem: People who don’t give a shit about other people’s children, and only change their ways once their reckless behavior has consequences for themselves.

  • Grass Chief

    National Highway Traffic Safety Administration found that drivers with a blood alcohol level of.08, the legal limit in most states, were 293% more likely to be involved in a crash. Such an educative post with lots of information.

  • Ed Wood

    Most, if not all careful studies concur that alcohol is more impairing than marijuana. But if you are one killed or injured by a marijuana-impaired driver, the statistics don’t matter.

  • Sarah Krebs

    What I’m wondering is if they will be taking more seriously the people on narcotics, antidepressants, anxiety meds or sleeping pills.. I know for myself while I was on these meds I fell asleep several times and have gone into the ditch, but with cannabis I am totally in control.