States with legalized marijuana see spikes in car accidents, fatalities

PISCATAWAY, N.J. — Legalizing cannabis in the United States is linked to an increase in car crashes and traffic-related deaths, according to a new study. Specifically, researchers say the number of fatal crashes jumped by four percent in five states that permit recreational marijuana.

The study reports that number of crashes that led to injury also rose by just under six percent in states with legalized marijuana. Meanwhile, the team did not see a spike in a comparison group of six states that have not legalized the drug.

Fatal crash rates rose by around two percent after cannabis became legal and by the same amount again when shops started selling the drug. Overall, crashes leading to injury rose by six and a half percent after legalization, but fell slightly once marijuana sales began in shops.

“The legalization of marijuana doesn’t come without cost,” says lead researcher Charles Farmer, Ph.D., from the Insurance Institute for Highway Safety in a media release. “Legalization removes the stigma of marijuana use, while the onset of retail sales merely increases access,” Farmer adds. “But access to marijuana isn’t difficult, even in places without retail sales. Users who previously avoided driving high may feel that it’s okay after legalization.”

The team believes the more pronounced relationship between cannabis and crash injuries, rather than fatalities, may be because some drivers slow down when they drive under the influence of marijuana. They create a larger distance between themselves and other vehicles. Motorists who drive “high” may not be able to avoid a crash at lower speeds, but the accidents that do happen are less likely to be deadly. Earlier studies involving driving simulators have shown that marijuana use can affect reaction time, road tracking, lane keeping, and attention.

Colorado car crashes up the most after legalized marijuana

For the study, the team collected data on traffic crashes and the amount of traffic in 11 U.S. states and from the Federal Highway Administration between 2009 and 2019. Colorado, Washington, Oregon, California, and Nevada all legalized recreational marijuana during the study period.

Arizona, Idaho, Montana, New Mexico, Utah, and Wyoming did not.

The authors adjusted their findings for factors known to contribute to crashes and fatalities, such as including seat belt use and unemployment rate. Colorado had the biggest jump (+17.8%) in crashes leading to injury and California had the smallest (+5.7%) after both legalization and the beginning of retail sales. Nevada’s rate decreased by 6.7 percent.

More fatal crashes occurred in Colorado (+1.4%) and Oregon (+3.8%), but the team found decreases in Washington (-1.9%), California (-7.6%), and Nevada (-9.8%). Dr. Farmer says states thinking about legalizing marijuana should ban people from driving while under the influence.

Researchers note their study shows a correlational, but cannot definitively prove legalized marijuana is responsible for the increase in road deaths and crashes. “Studies looking for a direct causal link between marijuana use and crash risk have been inconclusive,” Farmer concludes. “Unlike alcohol, there is no good objective measure of just how impaired a marijuana user has become. Until we can accurately measure marijuana impairment, we won’t be able to link it to crash risk.”

The findings are published in the Journal of Studies on Alcohol and Drugs.

South West News Service writer Gwyn Wright contributed to this report.


  1. Legalizing Cannabis will not create a massive influx of marijuana impaired drivers on our roads.

    It will not create an influx of professionals (doctors, pilots, bus drivers, etc..) under the influence on the job either.

    This is a prohibitionist propaganda scare tactic.

    Truth: Responsible drivers don’t drive while impaired on any substance period!

    Irresponsible drivers are already on our roads, and they will drive while impaired regardless of their drug of choice’s legality.

    Therefore, legalizing cannabis will have little impact on the amount of marijuana impaired drivers on our roads.

    The same thing applies to people being under the influence of cannabis on the job.

    Responsible people do not go to work impaired, period. Regardless of their drug of choice’s legality.

    There is absolutely no doubt now that the majority of Americans want to completely legalize cannabis nationwide. Our numbers grow on a daily basis.

    The prohibitionist view on cannabis is the viewpoint of a minority and rapidly shrinking percentage of Americans. It is based upon decades of lies and propaganda.

    Each and every tired old lie they have propagated has been thoroughly proven false by both science and society.

    Their tired old rhetoric no longer holds any validity. The vast majority of Americans have seen through the sham of cannabis prohibition in this day and age. The number of prohibitionists left shrinks on a daily basis.

    With their credibility shattered, and their not so hidden agendas visible to a much wiser public, what’s left for a cannabis prohibitionist to do?

    Maybe, just come to terms with the fact that Cannabis Legalization Nationwide is an inevitable reality that’s approaching much sooner than prohibitionists think, and there is nothing they can do to stop it!

    Legalize Nationwide!…and Support All Cannabis Legalization Efforts!

  2. What has actually occurred in states that have legalized cannabis is that law enforcement agencies statewide immediately and vigorously began a new policy of testing more drivers than they ever did before legalization occurred for residual trace amounts of THC. Which remain detectable in a driver’s system for up to months after consuming cannabis.

    This obviously in no way proves actual impairment at the time a driver is pulled over. So for instance, the police get to the scene of a roadside accident with a fatality. The driver at fault, is let’s say for example three times over the legal alcohol BAC limit, but the police also insist on a test for cannabis. Although bear in mind, with a BAC three times over the legal limit for booze and with all the obvious tell-tale signs of impairment, it’s plain for all to immediately see, and know, that alcohol was the drug responsible for this tragedy….

    Residual trace amounts of THC are detected in the driver’s system after the police conclude their very specific and intentional policy driven test for those residual trace amounts of THC. A month prior to being pulled over, the driver consumed a little cannabis socially with friends…

    Obviously, the joint or two from a month ago had nothing to do with this fatal and tragic accident, but the booze the driver drank at the bar before he got into his car that very same night most certainly did.

    Law enforcement now marks off this accident as another cannabis “INVOLVED” fatality in order to bolster their bogus statistics.

    Prohibitionists always use terms like “INVOLVED” , “RELATED” or “LINKED” when they tout these horrific sounding statistics and claims. Because they can’t ever prove cannabis impairment alone to be the actual “CAUSE”.

    In states that have now legalized cannabis, when you get into an accident whether at fault or not at fault even, pulled over for speeding or for anything at all, law enforcement policy will automatically also require that the police administer that very same test for residual trace amounts of THC from up to months prior to being pulled over. Which again, in no way proves impairment whatsoever and then the results are added on as just another one of their bogus cannabis “INVOLVED/RELATED”/LINKED” statistics.

    This is nothing more than merely another prohibitionist scare tactic. The goal being to frighten and alarm the public back into the strict prohibition of cannabis.

    Well guess what? The public isn’t buying it and everyone sees the deceit by ever more desperate prohibitionist zealots. Hell-bent on keeping cannabis illegal. So, the public is already well aware that when such claims are made about cannabis “INVOLVED/RELATED/LINKED” deaths, they are flat out lies!

    Nobody is so gullible as to believe these utterly nonsense prohibitionist claims of massive amounts of new cannabis impaired drivers.

    Now, I challenge all anti-cannabis prohibitionist types publicly yet again:

    Please provide us proof of just one single roadway fatality proven one hundred percent to have been “CAUSED” (Not “INVOLVED/ Not “RELATED”/Not “LINKED”) by cannabis impairment and only cannabis impairment, alone.

    The public is waiting for prohibitionists to provide indisputable proof of just one such death “CAUSED” directly and solely by cannabis impairment, alone. Just one. (Not even the massive influx prohibitionists claim. Just one.)

    We’ll wait….and wait…and wait….While we all know they simply can’t. Because it’s all just propaganda, lies, and scare-tactics.


  3. How many of these accidents were actually CAUSED by Marijuana use and not something else. I would like to see the actual studies showing that Marijuana CAUSED the accident.

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