Legalization of Marijuana Linked to an Increase in Traffic Crashes and Deaths

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A recent study has found an association between the legalization of marijuana and an increased occurrence of car accidents.

Could the legalization of marijuana be causing more car accidents?

According to a recent study published in the Journal of Studies on Alcohol and Drugs, states that legalized recreational marijuana had an increase in traffic crashes and deaths.

“The legalization of marijuana doesn’t come without a cost,” says lead researcher Charles M. Farmer, Ph.D., of the Insurance Institute for Highway Safety in Ruckersville, Va.

After legalization and the launch of retail sales, there was a 5.8% rise in the incidence of traffic collision injuries and a 4.1% increase in the rate of fatal crashes, according to Farmer and colleagues’ analysis of five states that permit people age 21 and older to consume marijuana recreationally. In a comparative group of states without marijuana legalization, the researchers did not see any rise during the same period.

Overall, the first increase in the injury crash rate occurred after legalization but before retail sales began. Injury rates from car accidents increased 6.5% following legalization, however, they marginally declined (-0.7%) after retail sales started. However, fatal accident rates climbed both after legalization (+2.3%) and after retail sales were legalized (+1.8%).

“Legalization removes the stigma of marijuana use, while the onset of retail sales merely increases access,” says Farmer. “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 sharper relationship between marijuana legalization and traffic crash injuries, rather than fatalities, may be due to how some drivers compensate when impaired by marijuana. Often, drivers under the influence of marijuana slow down and maintain a larger distance between themselves and other vehicles. Impaired but at lower speeds, drivers may not be able to avoid a crash, but the crashes that occur may be less likely to be deadly.

According to the authors, earlier studies involving driving simulators have shown marijuana use to affect reaction time, road tracking, lane keeping and attention. However, Farmer notes that the current study is correlational, and increased marijuana use itself is likely not the sole cause of the increases seen.

“Studies looking for a direct causal link between marijuana use and crash risk have been inconclusive,” he says. “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.”

To conduct their research, the investigators collected data on traffic crashes and traffic volume from 2009 to 2019 from 11 states and from the Federal Highway Administration. Five states (Colorado, Washington, Oregon, California, and Nevada) legalized recreational marijuana during the study period. A comparison group of six states (Arizona, Idaho, Montana, New Mexico, Utah, and Wyoming) did not. The authors statistically adjusted for factors known to contribute to crashes and fatalities, including seat belt use and unemployment rate.

The changes in injury crash rates varied by state: Colorado had the biggest jump (+17.8%) and California the smallest (+5.7%) after both legalization and the onset of retail sales. Nevada’s rate decreased (-6.7%). For fatal crashes, increases occurred in Colorado (+1.4%) and Oregon (3.8%), but decreases were found in Washington (-1.9%), California (-7.6%) and Nevada (-9.8%).

Farmer points out that states considering marijuana legalization should consider a few steps to help forestall a potential increase in crashes. “First, convince everyone that driving under the influence of marijuana is not okay,” he says. “Then, enact laws and sanctions penalizing those who ignore the message. Finally, make sure you have the resources (i.e., staffing and training) to enforce these laws and sanctions.”

Reference: “Changes in Traffic Crash Rates After Legalization of Marijuana: Results by Crash Severity” by Charles M. Farmer, Ph.D., Samuel S. Monfort, Ph.D. and Amber N. Woods, Ph.D., 19 July 2022, Journal of Studies on Alcohol and Drugs.
DOI: 10.15288/jsad.2022.83.494

21 Comments on "Legalization of Marijuana Linked to an Increase in Traffic Crashes and Deaths"

  1. “…, may be due to how some drivers compensate when impaired by marijuana.”

    The real problem is that there really is no way to compensate for unexpected situations where road conditions (such as a patch of black ice) or other drivers creating an unsafe situation, can be adequately compensated for when one’s reaction times are increased.

    I once knew someone who was a heavy user. He rationalized driving after smoking by claiming he compensated. However, my personal observation was that his conscious recognition of road hazards, such as a traffic light ahead, was that he took far too long to process the information. I was following his car and was already on my brakes long before he started to apply his.

    • I’ve noticed the exact same thing, riding with somebody after they smoked. It seems like weed doesn’t cause nearly as much visual impairment as alcohol but slows down your perception of time more.

  2. Honestly, it boggles my mind how long thc remains detectable in bloodwork. Long after the high has worn off. I think that makes it nearly impossible to test for thc like bac and have it carry much weight. It’s not all that different of a problem than some prescription pills, though, it’s hard to pinpoint exactly when somebody is high legally. Regardless, enforcing weed possession laws is a drain on law enforcement resources and I don’t see this as a reason to oppose either decriminalization or legalization, if somebody wants to get drunk or high and has poor enough judgement to drive impaired and commit DUI I doubt they’re going to be too concerned with whether the substance is legal or not as they’re already committing a crime.

    • “… it’s hard to pinpoint exactly when somebody is high legally.”

      Being over the legal limit is prima facie evidence that the person was impaired. One can be under the limit and still be impaired, and if impairment can be demonstrated by other means, the user can still be prosecuted. As with all drugs, there is a wide variation in the efficacy and side-effects and setting a limit so high that virtually everyone will be impaired, does not mean that some small percentage won’t be impaired at a much lower concentration.

      • I’ll admit, my phrasing was pretty poor but what I meant was that with alcohol it’s easy to test for. Alcohol leaves your system pretty quick. If you blow above 0.08 in most states, you’ll be arrested at a traffic stop no matter what. Thc is a lot slower to leave your system. I didn’t mean to sound like I’m defending driving stoned. For the record, I think driving while you’re impaired on anything is an awful idea and is little or no better than drunk driving. Point is, driving impaired on anything is already a crime, so why add another charge because the substance is illegal?

    • I didn’t mean that I condone high driving I think you misunderstood a bit

  3. And Xanax….? And Oxys…?

  4. Maybe a paid research/article to scare the public against marijuana legalization?

    Irresponsible people are keep using alcohol for so many traffic accidents & yet it is legal no problem!

    IMHO, overdose-safe drugs (like DMT, THC, LSD, Psilocybin etc) (which are actually safer than alcohol!) legally should/must be treated same as alcohol (which is really just another (similar) kind of drug)!
    IMHO, just like prohibition of alcohol had caused so much crime in the past (& that is why it was repealed many years later), prohibition of many similar drugs are causing so much crime today!
    We need to take lesson from history & end “War On Drugs”!!
    (Not to mention, (according to many medical research) drugs like DMT, THC, LSD, Psilocybin seem to be extremely promising against (major) depression & PTSD!)
    (& what benefits alcohol or tobacco have exactly (& yet they are legal)?)

    • “… overdose-safe drugs …”

      There are instances where early users of LSD had no idea what the safe limits were and suffered severe consequences. Even today, children get poisoned by THC because they have small body masses. However, the biggest problems are probably related to poor judgement and a break with reality while under the influence of mind-altering drugs. Thinking that one can violate the laws of physics (or not thinking at all!) will usually end badly. How many people have acquired incurable STDs while under the influence? The only ‘safe’ dose is where one’s judgement is not affected.

      Using potentially mind-altering drugs for medical reasons, under medical prescription and supervision, is NOT the same as recreational use where the user is not capable of sound judgement.

      The one thing that usually identifies users of recreational drugs is how quick they are to defend their behavior by rationalizing and unsound logic.

      • Alcohol impairs judgement and has led to countless incurable STDs. Does that mean booze should be illegal for everybody no matter the circumstance? It really comes down to personal responsibility. If somebody gets high/drunk and drives, that’s their fault. The drug didn’t force them to drive and there should be consequences. Why penalize everybody else for the actions of a few, especially considering weed isn’t exactly hard to get illegally

        • Really, the issue of drug legalization is similar in a roundabout way to guns. A gun doesn’t jump up and kill somebody on it’s own, so why are drugs thought of that way?

          • Clyde Spencer | September 1, 2022 at 8:39 pm |

            “… why are drugs thought of that way?”

            Because many recreational drugs are psychologically addictive, if not actually physically addictive, they are not like guns.

            Libertarians refer to illicit drug use as a victimless crime. However, it is rarely the case people around the user are not impacted. Even in states where marijuana has been legalized, there are still problems with environmental damage from large growing operations in the National Forests, and sometimes hunters are killed inadvertently by the growers protecting their cash crop. Those who use recreational drugs carry moral culpability for the unintended consequences of growing and distributing drugs. Handgun Control Inc used to use the motto “No price it too high to pay if it saves even one life.” The corollary to that is if even one life is lost from the use of recreational drugs, the price is too high.

          • Clyde Spencer | September 3, 2022 at 8:53 am |

            “It isn’t stopping anyone from using.”

            I think that it would be more accurate to say that penalties aren’t stopping everyone from using. It is like saying we should do away with punishment for murder because, despite the threat of punishment, murders still occur. However, were the severe punishment to be eliminated, undoubtedly there would be more murders. No law is perfect. The question society needs to answer is whether the net results are positive or not. As long as there are negative effects, from using non-medicinal drugs, on people other than the actual user, then society has a vested interest in trying to eliminate or at least reduce the usage. Children accidentally consuming an adult’s recreational drugs are sufficient reason alone to sanction non-medical or non-nutritional drugs.

          • Clyde Spencer | September 3, 2022 at 3:22 pm |

            I must confess that I have a streak of libertarianism in me and tend to agreee with most of what you say. However, the problem I see with drugs is that “No man is an island.” What if you are ‘tripping’ and someone has an emergency that requires immediate medical care, and you aren’t up to properly applying a tourniquet or CPR? What if you try to take them to an emergency room yourself, and you have an accident on the way, which kills a stranger? What if, despite your best efforts, your kid finds your stash and dies from it?

            There is also the moral cupability in that as a user, you help create a demand for a drug that leads to the business success of Mexican Cartels. Because there is so much potential profit in drugs, the growers and distributors go to extreme measures to protect their operations and products. That sometimes leads to the loss of lives, and even in the case of states where the product is legal, there is commonly environmental damage because of the appropriation of water, the use of herbicides and pesticides to increase their yield, and urban gang warfare over turf distribution rights.

            You present the argument about net results of enforcement versus personal effects. Let me tell you a story. Back in the ’70s I knew a guy who was a graduate aeronautical engineer from MIT. He was living on welfare and what he could make from his hydroponically-grown ‘grass.’ He eventually was losing enough ground financially that he felt he had to find a good job. With his degree, he had little trouble finding a job with the Bay Area Rapid Transit. However, he quit after two weeks. It was not just his personal loss of income, but society lost what he might have contributed because he’d rather get high than work 40 hours per week.

            A rule I try to live by is to think of what the world would be like if everyone were to act as I was about to act. In his case as a role model, the world would literally “go to pot.” He could manage his marginal life style only because other people were willing to work to provide him with the things he needed to survive.

            I think that anyone who feels that their choice of using recreational drugs doesn’t harm anyone is only rationalizing.

        • Alcohol has an interesting and unfortunate history. For thousands of years it was safer to drink wine, mead, or beer than water. Greeks and Romans drank their wine diluted with water, with the wine acting as a disinfectant. Because alcoholic drinks have been used so widely and for so long, it has a special place in society, even being a core of the sacrament in Christian religions. Yet, especially in more modern times, alcoholic drinks have done a lot of harm. Were that not the case, Prohibition would not have passed. We can’t undo our history. However, excusing the relatively new problems from recreational drugs as being just like alcohol is a mistake. It is a conundrum because Prohibition was an utter failure, yet the problems of alcohol are still with us. I don’t know what the answer is, but I don’t think it is throwing the doors wide open and saying “anything goes.” A Roman party-goer could usually walk home. That rarely happens in today’s world.

          • You’re absolutely right on the first part, people didn’t understand that the process of boiling made water safe to drink, but I think people would be better off to view drugs and alcohol use as a public health issue rather than something to punish users for in jails that are already overcrowded.
            If a drunk or high person does something else illegal, then by all means they should be prosecuted for that crime the same as if they were sober. Being impaired shouldn’t excuse bad behavior. It might factor into it, but it’s up to the individual to make choices about what they put into their own body. But what good does jailing drug users do? It isn’t stopping anyone from using. Why not just inform people of the risk, and let them make their own choices.
            Nor should it be the government’s job to enforce moral behavior. It really makes no sense to take years of a person’s life away for something that can’t physically hurt them and claim it’s for their own protection, which is what is going on with marijuana.
            Portugal decriminalized small amounts of even hard drugs in 2000, but has not seen an uptick in violent crime.

          • Murderers are a threat to public order. If murder were allowed and murderers went unpunished than I would imagine that the family of the victims would seek out vengeance and that would lead to additional killings. Similar story with other crimes against another person.
            A murderer has committed the most serious crime possible (first degree murder) and there really isn’t any reason for them to conform to any other laws of society. It’s the job of the legal system to provide fairness not enforce morality. It’s legal to cheat on your wife but immoral. 🙂
            I’m talking about decriminalizing drug use, not sale for anything harder than marijuana. Anybody that is willing to sell poison to make a quick buck needs to be held to consequences for it. As far as children gaining access, it’s extremely irresponsible for a parent to leave drugs laying where a kid could access them (wanton endangerment).
            What about people that don’t have kids, though? If a single person with no kids wants to sit at home and smoke weed for fun is it fair to raid their home because somebody else put their kids in danger by bringing drugs around them ? Not a very productive use of time, then again so are a lot of things. A lot of things are dangerous to children as well but legal. Firearms, knives, bleach, plastic bags, etc. Most of those things come with warning labels, and if weed were legal to sell it should also come with a label, too, as well as penalties for underage use, as there is with alcohol.
            With marijuana, I think you could argue the negative effects from enforcement outweigh the effects from the drug itself.

      • You’re pretty intelligent, and I’ll say you have a fair point on the bit about society losing the guy’s contributions. It takes a lot of money to buy pot, and when somebody loses their job or can’t get one because of a drug habit it can be so psychologically addicting that they resort to stealing.
        I also don’t buy it when I hear weed smokers think that smoking makes them better at something, nor the “it’s just a plant” line. Opium is a plant too, just because something is natural doesn’t make it harmless. Weed isn’t nearly as harmful as opium imo as it’s not physically addictive, but it still is habit forming.
        I’m not a heavy smoker, I’ve only ever tried it a couple times at parties and it made me a bit anxious. I think the anxiogenic effect would deter some from it.
        I know people that love it, though, and I hate for them to be punished the same as if they committed a violent crime like an assault.
        As far as the part about somebody having a medical emergency, though, a lot of times drug users are hesitant to call paramedics because they’re afraid they’ll be caught with drugs. If it were legal, they might be more inclined to call 911 instead.
        I think legalization would help remove a major source of income from cartels, the “high” 🙂 (pardon the pun) supply might drive down black market prices.
        Weed now has more THC compared to the past, but prohibition has driven that somewhat. People want the strongest possible high from the smallest amount in places where it’s illegal, because it’s so risky to possess a larger amount and having less availability.
        I think nearly all US states will, at some point in the near future, completely decriminalize or legalize weed. I live in a socially conservative state (Kentucky) that probably be among the last to do so.

  5. Lies. No proof. Compare to alcohol which is 100 times worse. Thie article written by Republican GOP authoritarian dictator!

    • Speaking of “No proof,” where is the proof that “Thie [sic] article written by Republican GOP authoritarian dictator!”

      Apparently the rationalization by users that they can compensate for being ‘stoned,’ doesn’t end there.

  6. “Marijuana linked” does NOT equal “marijuana caused.” — This is a trick first devised by Colorado narcotics police who were fighting against that state’s legalization. This is what happens. – An unfortunate, NON-impaired marijuana consumer gets crashed into by a drunk, texting or other bad driver. – Everyone in all the cars gets tested, even the passengers. If just one person tests positive, or if they find a small amount of marijuana in one of the cars… Shazaam! – You have a “marijuana linked” accident. – Which gives you a mountain of bogus statistics.

    Marijuana is not alcohol. The preponderance of the research shows marijuana consumption is not a significant cause of auto accidents. — In 2015, the NHTSA, found that while drunken driving dramatically increased the risk of getting into an accident, there was no evidence that using marijuana heightened that risk.

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