Study: Cannabis’ Influence On Driving Performance Differs Significantly From That Of Alcohol

Cannabis-influenced driving performance is significantly different from alcohol-induced driving behavior, according to driving simulator data published in the Journal of Applied Toxicology.

Investigators with the National Institute on Drug Abuse and the University of Iowa evaluated simulated driving performance in subjects following their consumption of vaporized cannabis, alcohol, or placebo.

Researchers reported that cannabis administration was associated compensatory driving behavior, such as decreased mean speed and increased mean following distance, whereas alcohol administration was associated with faster driving. Their findings are similar to those of other driving studies, like those here and here.

Investigators also reported that cannabis dosing in combination with low quantities of alcohol “mitigated drivers’ tendency to drive faster with alcohol” – a finding that contrasts with prior data acknowledging that the two substances combined typically possess an additive adverse effect on psychomotor performance.

“THC concentration-dependent associations with decreased speed, increased time below the speed limit and increased following distance suggest possible awareness by drivers of potential impairment and attempts to compensate,” authors concluded. “The compensatory behavior exhibited by cannabis-influenced drivers distinctly contrasts with an alcohol-induced higher risk behavior, evidenced by greater percent speed.”

According to the findings of a recently published literature review of crash culpability studies, “[A]cute cannabis intoxication is related to a statistically significant risk increase of low to moderate magnitude [odds ratio between 1.2 and 1.4].” By contrast, a 2015 case-control study by the US National Highway Traffic Safety Administration reported that driving with legal amounts of booze in one’s system is associated with a nearly four-fold increased crash risk (odds ratio = 3.93).

An abstract of the study, “Cannabis effects on driving longitudinal control with and without alcohol,” appears online here.

38 thoughts

  1. Those most responsible among Stoner Society are, of course, all in favor of public and personal safety. And, yes, impaired driving, regardless of the reason for impairment, is clearly dangerous. (Full disclosure, I used to drive drunk. Lost my license. I was impaired. And I was in the wrong. And I regret it. And I don’t do it anymore.)

    However, having said all that, I feel I must now call for a reality check here. This might not be popular, but surely it is true: DRIVING ITSELF is the threat we’re actually discussing here!

    Reality check: neither a drunk nor a stoner is particularly dangerous by themselves, absent powerful tools or technology. Okay? Am I right? It’s the 4,000 pounds of metal moving at high speeds that will fuck you up! And that is true even if you were not impaired in any way. That in no way makes you safe.

    The human body is only evolved to take a hit (from, say, a tree branch) at top running speeds of, say, 10 MPH or so? Now, that’s not intended to be precise; my point is simply that DRIVING A CAR is dangerous at any speed, under any driving conditions, regardless of any degree of impairment.

    There is NO SUCH THING as “safe” driving!

    I’m not advocating for horse-and-buggies, or anthing else, other than the simple truth. It’s just a fact. Strap yourself to a gigantic chunk of metal and launch it through space at high speeds, and you’re putting yourself and everyone around you in danger! (Please don’t get mad at me, I’m not making this up, you know!)

    It might not be a popular view in our driving-oriented culture but, clearly, it’s the automobile that’s dangerous to society, not the drugs.

    1. Those are good points. And while self-awareness of impairment could result in safer driving behavior, what the study fails to address are judgment, situational awareness, and reaction times. The study does NOT say driving stoned is safer than driving drunk – it only says stoners tend to try to compensate. Even driving clean is dangerous if your head isn’t in the game.

      1. Within a couple years all driving will be performed by computers. Driverless cars are being introduced as we type. There will be no need for traffic cops. This article will soon be obsolete.

      2. I would rather arrest the wheel of a drunk driver or passenger myself to the most stoned-high person I will ever meet in my life than surrender my vehicle to an automated “intelligent” or remote-controlled vehicle.

    2. the only case in which your argument may be valid is in the case if someone is driving a car that’s not up to ideal standards and can be prone to some sort of accident like breaking down on the highway. Because ideally, if everyone were to comply with traffic laws and general guidelines, there is no way there can be injury, no matter how new cars are to humans as a species. What makes cars dangerous is humans, since we are prone to error. We forget to put our signal, we don’t look before we turn, we don’t stay behind a car at least a cars length away, we don’t slow down in certain time, or we impair our bodies with drugs that affects our rational mind. That’s what causes the impact generally.

      1. With respect, I disagree. There is no such thing as an “ideal” driver, because “to err is human”, or put another way, “nobody’s perfect.” Further, there’s no such thing as a perfect car, or perfect driving conditions. That’s why driving is always dangerous. There will always be unknown variables and unaticipated situations.

        In the real world, driving an automobile always involves risk of injury or death, regardless. It’s inherent to the action. Driving impaired obviously increases the risk of injury while using an automobile. But there is no way to guarantee a safe drive to anywhere.

        It is the car that’s dangerous, not the drunk. Without the car, the drunk is a pushover. But any moving vehicle represents a serious risk.

      2. You must be kidding. You have heard of things like deer in the road, right? How about rock slides? How about icy roads, ever heard of them? What about tires blowing out and flying across the highway and landing on the hood of somebody else’s car? I could go on but I think you get the point. That’s why they are called ‘accidents’.


    Even the ‘I drive better stoned’ argument is,
    however unlikely, proven at least somewhat plausible.

    There are no good arguments against
    legal, taxed, responsible, adult cannabis usage.

    Why incarcerate productive members of society for this gift?

    1. I could make an argument against the government taxing it or regulating it in any way, in The Land of The Free, but yes, it should be legal.

  3. Cannabis helped with my alcohol abuse… That was 20 years ago… Necessity of need … I get what I need and I need what I get … Suffering isn’t tamed by laws but by medicines from plants …

  4. We are ushering in a new era of driverless cars. Excuses for safe driving will soon be of the past. There will be no DUI’s or tickets or getting pulled over for illegal lane changes. The reefer madness dooms day scenarios are a thing of the past. The politicians need another source of revenue such as legal cannabis. Maybe the laid off cops can find jobs I the industry. People in their late fifties or older have no business voting because the young people then have to deal with the messes the leave behind once they are gone due to illness or death.

    1. As a 60 year old I still care a great deal about what happens in this world. I try every day to live a good life and to make this world a better place to live in.

      You need to get over your age related predjudice and grow up!

    2. There are many of us over 50 who balance out the under 50 impetuousness. I am a chronic. I am for legal Cannabis I am for mild regs & low taxes on it. There is no reason for you to be ageist.

      1. The problem is that not all old guys think like you and most of them are nosy. The younger generations are the ones left holding the bag because of the messes you create. On the other hand, the young people are stupider since they do not make it a point to go vote and counter your mess.

      2. Thankfully, not all younger people think like you!

        The fact is that age has zero to do with the way someone thinks. One major factor is that prior to 25 years ago people had much less access to information compared to now; the internet age. People believed the lies the Govt told them and had little to no resources to dispute them. Trust me, the Govt has told the public many lies over the years! They continue to do so but they’re a bit more careful now.

  5. The findings of this study support what most of us have already known for years. I think this data suggests, strongly, that the penalties for DUI cannabis should be less severe than DUI for alcohol.

    In an ideal world, regardless of what someone has in their system, the actual level of impairment, if any, should be the only factor that matters.

    Sadly, this world is far from ideal. In this world, the powers that be, stopped the Cannabis Cup from taking place in Colorado.

    1. Actually, if you follow the logic, there should be a bonus paid to any individual found driving with thc in their system. these documented behaviors of lower speed and increased distance between vehicles support my theory that NTSB safety records x marijuana permissiveness=decrease in driving accidents and fatalities. Any driver safety education course advocates exactly what marijuana-influenced drivers are shown to do: drive slower and allow more space between vehicles.

      Rather than view this behavior as “compensatory for impaired state” perhaps the reality is that being stoned makes you more perceptually aware of what the dangers are, and you realize what many drivers seem oblivious to, which is the fact that mishaps can happen out of nowhere and in the blink of an eye, and these behaviors allow more time for reaction.

      1. I totally agree!! As a professional drunk driver and long time toker, I can say for sure, cannabis is safer because the driver is more aware/acute — not less aware/acute…..

  6. A peer based review in the Journal of Applied Toxocology with the support of NIDA? The same NIDA that Senators Booker and Gillabrand were complaining prevent research on marijuana in the previous blog? Next youre gonna tell me it snowed down in Central Mexico. (Waitaminute… apparently it DID snow as far south as Guadalajara…) Ok fair enough.

    I’m so glad that these studies are being conducted with placebo alcohol and marijuana variations. It’s so important to be ale to refer to the difference.

    Last night was poker night, and I was mixing some blueberry weed with some scottish ale. It’s not recommended to mix marijuana with alcohol, especially among novice consumers, but nonetheless it happens frequently at parties, poker nights and barbecues across America, so here is a suggestion;
    Bring only enough beer for yourself that is a quality that will get you where you want to be but not too much… then finish the night with your favorite herb, but preferably a sativa with pinenes like Trainwreck or Jack Herrer strains. Indicas tend to add to the couchlock effect and mixed with alcohol can create lethal fatigue for the drive home.
    The most important thing weed does for me is it restores my perception that alcohol took away. Also, weed’s stimulation of appetite or provoking one to just drink some water prevents the ill effects of alcohol.

      1. …To be “ale” to refer to the difference,” …that’s the best typo I’ve ever done!

  7. Point well made here: SUBSTITUTING cannabis for alcohol will save society $Billions, prevent thousands of violent deaths.

    Now think further:

    How many times did a dangerously drunk person count on “a $igarette or two” to sober up enough to drive the car home safely?

    How many times did such a postmedicated drunk run out of $igarettes and maybe drive on unfamiliar streets searching for a place to buy them?

    $igarettes may contributorily cause a surprisingly high percentage of the accidents attributed to alcohol! Cannabis SUBSTITUTING FOR $IGARETTES may be a big part of the answer– the drunk will THINK TWICE (or twice as fast) and Delay Driving in everyone’s interest.

    Re Mark Mitcham’s point about automobile
    unsafety, maybe the rescuing aspect of cannabis is that it makes a person more sociative, more capable of enjoying friendly conversation with real strangers on a
    BUS rather than sitting armored in one’s personal or only own-family hitcar like petty bourgeois do!

    Julian, we should pressure beer and wine companies to market L24MB Little 2- and 4-ounce Mod(moderation)Bottles which after use instead of thrown away can be made into a new product such as education toys or music instruments.

    1. Mexweed, you got me!
      I don’t even own a car anymore, haven’t for years. I’ve learned to do without one. And I never get pulled over for driving impaired! And I never worry about driving over a pedestrian. I worry about BEING that pedestrian now!

  8. “Researchers reported that cannabis administration was associated compensatory driving behavior, such as decreased mean speed and increased mean following distance, whereas alcohol administration was associated with faster driving.”

    WOW man! There’s a moral there somewhere.

  9. I’m alive today because of the other guy that was watching out for me.

    Go slow in the snow.

  10. We are ushering in an era of driverless cars. There will be no need for traffic cops and the source of revenue from DUI’s, illegal lane changes, etc. will be depleted. Revenue Legal cannabis can fill the gap and ex-cops can get jobs manicuring buds. REEFER MADNESS DOOMS DAY SCENARIOS ARE OVER. Politicians that support prohibition need to be voted out.

    1. I’ll tell you what eelo; You go ahead and get in one of those automated google cars without a human driver or a break peddle. Just don’t spill your rolling tray when that trailer ahead of you loses a tire that subsequently bounces off the asphalt and takes flight as you’re sitting in the back rolling a joint watching the tire go airborne from the front windshield straight for your slack-jawed face while your automated car calmly proceeds in line with the path of impact, unable to detect the danger.

      Good luck with that.

      I’m 37 and looking at both ends of the spectrum with youth, age and marijuana legalization and I have to say your youthful faith in technology makes me thank God that I remember a time before cell phones when we had to settle our compulsive decisions and meet and reason in person to conduct business and make important decisions …And our stupid shit didn’t get recorded.

    2. If we’re going to have bars with parking lots, driverless cars sounds like a good idea.

      1. galileo, there are three ways to deal with drunk drivers; the designated sober driver, the darwin award, and the firing squad. Believe it or not, there are a couple of countries where the last has been very effective at preventing recurrences of fatal drunk collisions.

  11. Any number of things can distract human drivers. Humans shouldn’t be driving.

    Driverless cars have 90% fewer accidents than human drivers – and that’s just with the tech we have today.

    1. It’s physics vs biology: humans shouldn’t be moving at a greater MPH than they can afford to take an impact!

      Here’s a common sense solution: Let the goddamn automated “driver” go to the store for cigarettes, at 80MPH, without you! You stay safely at home. So when two idiot automated “drivers” crash into each other, totalling both vehicles, you only lose a pack of cigarettes, not your legs or your life.

      “What about my job?” you protest? All I can tell you is, we Humans ain’t too bright! We put everything we need out of our own reach. Brilliant. Now it’s too far away to get to without putting everything we value (our lives, our kids lives) on the line. And somehow we’re shocked when there’s an accident. We’re just not living in the real world.

      You decided to “go for a drive,” and it’s Game Over, just like that. George Carlin channels the thoughts of a driver facing imminent death: “WHAT? HERE, NOW, ON THE FREEWAY??”

    2. And I suppose you think that these “driverless” cars are maintenence free and fix themselves? Say, how do you stop an automated car with no brake peddle when it loses power? … With the front end of another moving vehicle, obviously!

      You’re gonna need your weed to get McGuyver on your little google car once some hacker shuts your car down so the dealer can charge you a $150 “diagnosis.”

      I’ve got another idea; Why don’t we moderate our consumption of alcohol with legalized marijuana and drive home safely and responsibly?

      (Jeez, who are these trail horses? It’s gotta stink all up in up in the next horse’s butt…)

  12. I would like to apologize to my fellow bloggers for my strong language and opions over automated driving while rolling a joint in the back seat of a brakeless vehicle. If its of any consolation, before we shove ourselves down vacuum tubes across America, (which God only hopes, will be hotboxed with marijuana smoke and vapors) consider this factor before driving:

  13. What is so puzzling? people slow down because:what the f is the big hurry.{figure out how much time saved going that extra speed]. very to the reason of following to close and speed; the brain is allowed and made aware that this is DANGEROUS.

  14. This is an interesting study about driving under the influence of marijuana. I’m surprised to see that there was an increase of awareness under it’s influence. Thank you for sharing this study!

  15. Honestly if you think people getting cannabis is fair let me tell you first hand the only people you are really hurting are the cancer paitents, the veterans, the kids, the parents, the workers, and pretty much everyone else who uses cannabis already as part of their daily lives. So while this may seem well deserved and a joke to a lot of you, in a lot of ways it’s really not.

    It’s not Canadian for you to be ignorant and say don’t smoke and drive because that’s not a very good way of approaching something you don’t know anything about.

    If you don’t understand what it is doing and how it is affecting people why didn’t you ask? Why is it so hard to just say it how it is?

    Cannabis is 100x’s safer than most substances.

    There is no correlation between blood level and accute impairement while though it may cause drowsiness and possible side effects in some, for medical users it does not affect them the same way.

    While you could have chosen to introduce a condition C for cannabis on your Class 5 license, instead you just indiscriminately champion a new safety bill that just criminalizes the use of cannabis.

    That is not legalization. That is giving lawyers, insurance companies, the government, and law enforcement more money than it’s worth.

    Criminalizing people’s use of this substance is not Canadian and it is not right.

    I may be alone in this fight but as long as I think I am allowed to speak freely in this country so it shall be said:

    No one should lose their jobs over cannabis!

    The government needs to do more to legitimize the cannabis community and to apologize to the community for it’s years of punitive charges against anyone who has ever used cannabis.

    Please share this and stand up to what you know is wrong and add your name to this fight.

    Don’t let them tell you how to use your medicine when you know the truth.

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