The Great Marijuana Myth: Is Driving High Dangerous?

A recent study finds that drivers who smoke marijuana within a few hours of driving are more likely to get into an accident than sober drivers. Find out how much more.

Marijuana plant

Last week, the British Medical Journal published a study about the effects of smoking cannabis (aka marijuana, pot, weed, Mary Jane) on driving ability. Researchers at Dalhousie University in Nova Scotia, Canada, analyzed 9 prior studies and concluded that — contrary to most pot smokers’ beliefs — driving high leads to a higher risk of car accidents.

Now, before we go any further, let’s address the elephant in the room: pot is illegal in most states. But (as we know) people smoke it regardless of what the law says. However, no matter what folks tell you, driving under the influence of any controlled substance is illegal and dangerous.

We could write endlessly about reckless driving — drinking, using a cellphone, and even driving tired all put you and others at risk — but for our purposes today, let’s focus on Dalhousie’s study and the specific dangers of smoking pot and driving.

Weed and driving effects

Turns out, drivers who smoke marijuana within a few hours of driving are almost twice as likely to get into an accident as sober drivers. And though the accident stats aren’t as bad as they are for drinking and driving, the risk is palpable.

While alcohol is still the most common accident-inducing substance, a recent survey quoted on the National Institute of Drug Abuse’s Web site found that 6.8 percent of drivers who were involved in accidents — most of whom were under 35 — tested positive for THC (the chemical found in marijuana).

Smoking weed and driving laws

Unlike testing for alcohol levels, researchers and law enforcement officials have not yet determined how to accurately test for levels of marijuana intoxication. Many states, however, have begun to take a hard line on this public safety issue and police officers are now being trained to detect signs of marijuana intoxication. And make no mistake about it: driving a motor vehicle while under the influence of drugs — including legal-use marijuana — is illegal in all states.

Get a breakdown of drugged driving laws here.

The great marijuana myth

It’s possible you’ve heard a pot aficionado state:  “I’m a better driver when I’m stoned.” Not true. A major issue with drugged driving is that when you’re high (well, not you specifically, we know you’d never do that), you don’t always realize that your judgment is impaired. This is especially true for teenagers who are already at-risk drivers. Couple this with a few hits of ganja, and the buzz can become, well, killer.

Though it varies by person, it generally takes at least 3–4 hours to come down from a high. No amount of strong coffee or greasy food is going to sober you up faster.

Drinking and driving vs. smoking weed and driving

Most of us grew up hearing “don’t drink and drive,” but not nearly as much effort was put into preventing the combination of smoking pot and driving. Yet marijuana affects reaction time, spatial sense, and perception — all of which are crucial to safe driving. So when a person is driving high, they may end up following another car too closely (and brake too late), make unsafe turns, or misjudge road hazards.

RELATED: The Drunk-Driving Debate: .05 versus .08

The fact remains: weed and driving don’t mix

In the coming years, we may see a move toward the legalization of pot. But no matter where you stand on the issue — “a need for weed” or “not for pot” — we should all be on the same page when it comes to designating a driver who abstains from ALL mind-altering substances (legal or not).

If you’re into graphs and footnotes, you can read the whole British Medical Journal study here.

Related links

Driving on drugs: stats and facts
National Institute of Drug Abuse article on drugged driving
National Institute of Drug Abuse research report on marijuana abuse
CNN reports marijuana nearly doubles the risk of collisions
Dalhousie University report

321 Responses to “The Great Marijuana Myth: Is Driving High Dangerous?”

  1. JA
    February 17, 2013 #

    Wow, this article is absolutely retarded. In my younger years, I admit I was stupid and would get totally drunk then drive home. I was incredibly reckless in doing so because I was all over the road. Couldn't even remember getting home at times. Since I started smoking on a regular basis, I can say that I am so much more aware of what I'm doing while driving stoned. This article or any article have yet to prove that pot is as bad as "they" claim it to be. Get some real science done already and find a cure for cancer and diabetes.

    • thedudeabides
      March 3, 2013 #

      You are an idiot. Of course you think you are more aware when you are stoned. How often are you being more aware? Only when you think you need to be. Don't lie and tell us you are aware all the time. In addition, reaction time is slowed significantly with pot. So as aware as you might be, you're not on a position for optimal reaction.

      • oldemastiff
        March 23, 2013 #

        And how many "stoners" do you personally know or have hard facts on that have been in accident? And I hope someone who has nothing better to do than to actually name call would have some factual evidence to present to all us "idiots". Because these idiots do have called hard facts, unlike you. If you are going off on others, have some evidence or just read the posts and keep you mouth closed on a subject you have no business dicussing. And a good day to you.

  2. Maxpo
    February 17, 2013 #

    Let me preface this by stating that I am an advocate for the legalization of marijuana and every other drug, even ignoring the sound arguments pertaining to economics and enforcement. Plain and simple, an adult should be allowed to do as he pleases with his body. But only as long as he's not hurting anybody else. To wit, if the the marijuana law reform community ever expects to be taken seriously, its members must stop insisting that driving high is OK. Being stoned is an impairment, as is being drunk, sleepy, angry, distracted, geriatric, etc.

    That being said, the notorious 6.8% figure is not only murky (for reasons well-elaborated in previous posts), but STATISTICALLY MEANINGLESS without comparing it to the general population of drivers. In other words, What fraction of all drivers would test positive for THC? If it's less than 6.8%, this would suggest, though not imply, that recent (i.e. within the testable range) consumption of marijuana predisposes you to accident involvement. On the other hand, if it's more than 6.8%, this would suggest that recent marijuana consumption actually keeps you safer on the roads! As these data are unavailable, the cited figure serves only to obfuscate the situation.

    And, may I add: Hey hey hey hey… smoke weed every day.

    • Lauren Logan
      February 18, 2013 #

      I agree with your position that smoking pot and working or driving is not prudent. If don't support legalization in a responsible way. It is not safe to assume everyone will be able to use good judgment when driving when high. The comments about driving high (including mine) are intended to say that there it is no guarantee that it will cause accidents. It is important to realize that when people buy pot illegally they can be unknowingly supporting the drug trade into the U.S. We have been putting people in jail and spending too many dollars attempting to control something that could be more effectively controlled if it is legal.

    • Heathen
      February 20, 2013 #

      You're wrong, just as this article is wrong. This lady works for an insurance company, do you really think they would post an article that states driving stoned makes you a better driver, of course not. This article is garbage and has no facts whatsoever. 6.8% is an irrelevant statistic, they don't know if those individuals would have still been in a wreck even if they were sober. Too many conflicting influences to actually say that those 6.8% were due to the pot. And 6.8% what about the other 93.2% of wrecks were they sober? Too me that's a statistic that supports saying driving stoned you have a lower chance of having an accident. Lololo terrible article, terrible writer, why did I even waste my time reading and responding. In general WEAK!!!

    • juan
      February 23, 2013 #

      I can agree it is an impairment for thise with low tolerance who smoke skme grade a kush. For you and me, smoking blunts ever day has resulted in a drastically reduced high. Everyone who smomes knows people drive more cautiously when stoned, and you cant say that about alcoholics, pill poppers, or teenagers. Nicely worded post, but I dont think you are doing anyone justice by encouraging these people to embrace their misconceptions.

    February 18, 2013 #

    They can't fix phones either! I operate a small business repairing smartphones and its like they are smoking stupid instead of pot. It's a total joke when a pothead returns from lunch after smoking pot and tries to do a repair!

    • Irie-ITES
      February 20, 2013 #

      Herb heals .. Alcohol kills!!!

    • juan
      February 23, 2013 #

      Has it occurred to you that some people are just stupid? Plenty of sober people like that too. Maybe you are stupid for hiring stupid people? Funny, you will let stoners work for you, but here you are whining about them. Sounds made up almost.

  4. boheme19
    February 20, 2013 #

    Are you people serious? Do we really need to question whether or not driving stoned is a danger? And are you people seriously defending the idea that it's not? Get real. Some people will argue a point even when they know in their deepest heart that they're wrong, just to be right. Or sometimes I think they just get off on the thoughts of the shock value. What you don't realize is that you aren't really shocking anyone with what you think are your outrageous views. Other people only think you're an idiot.

    • Tony
      February 21, 2013 #

      You know I find the irony in your comment about who can't admit when they're wrong. It's you prohibitionists that can't stand the fact that driving stoned DOES NOT impair your ability to drive safely and effectively. Maybe it's you who should look in the mirror before you start calling other people idiots…

      • Storm Crow
        March 6, 2013 #

        Tony, You might want to read these other articles. First one is put out by an insurance quote provider-"Reasons Why Marijuana Users Are Safe Drivers". BusinessInsider provides "It Turns Out That Smoking Marijuana May Actually Make You A Safer Driver. While PRWeb, goes even further, "Marijuana Users Are Safer Drivers Than Non-Marijuana Users, New Study Shows".

        The United States National Highway Traffic Association (NTHSA) evaluated 32 subjects' driving performance after cannabis inhalation in high-density urban traffic. Investigators reported: ‘Marijuana … did not significantly change mean driving performance. "The study "Visual Search and Urban Driving under the Influence of Marijuana and Alcohol" found "Performance as rated on the Driving Proficiency Scale did not differ between treatments. It was concluded that the effects of low doses of THC … on higher-level driving skills as measured in the present study are minimal."

    • juan
      February 23, 2013 #

      Yes, we are saying that you are wrong. You fail to realize that you are spewing 50 years worth of brainwashing. You pass stoned drivers all the time without even realizing it. There are plenty of tests that have been done that contradict this one that werent done by people who profit from prohibition (or jacking up rates in weed legal states). You are a prime example of how Americans think their feeling of being right trumps facts, experience, and true justice and equality for all. If you drink coffee, which you probably do, then you are a drug user and shouldnt be driving.

      • J. Law
        March 6, 2013 #

        Ah Juan. And what lovely country do you call home? I'm going to ignore the American comment for now, and only address the last statement you made. Caffeine is not an illegal drug. However, if someone were to consume so much caffeine that it impaired their driving ability, then sure THEY shouldn't drive. But please, try not to waste our time with weak arguments that YOU have no FACTS to back up. After all, my American time is consumed fixing the problems of other countries. For example, the DRUG trade in Mexico and other countries south of the border. ;) once again sir your argument, is invalid.

    • Ben
      February 28, 2013 #

      To this I say… the government in it's infinite wisdom, prescribes me Adderall and Klonopin for my ADHD. Adderall is amphetamine salts (legal meth) to focus during the day, and Klonopin a barbiturate (legal heroin) to calm down and sleep as I have ADHD related insomnia. The fact is if I take a couple puffs of marijuana before class, it slows me down and I can focus and if I smoke a joint or 2 before bed I can sleep. On marijuana I had a 3.87 GPA and made the dean's list. On Adderall and Klonopin I had a 3.83 GPA and did not. So is the government right, should I take meth and heroin everyday? Or am I right self medicating on much, much, much softer drugs (I qualify for medical marijuana in all non-terminal states). Boheme19 are whats wrong with this country. You parrot things you've heard without learning the truth and hold onto ideas proven to be wrong. Stop believing the lies and pick up a newspaper for once in your life. 50 bucks says you're a republican.

        March 6, 2013 #

        Hey Ben, there are plenty of republican stoners. Chill with your political stereotypes.

      • huh
        March 9, 2013 #

        The _government_ prescribes your medication? Hmm, I'd check with a _doctor_ if I were you.

      • Tony
        March 11, 2013 #

        He is right in a sense. Especially when Obamacare comes into effect this year.

      • Maxpo
        March 20, 2013 #

        Adderall is not meth, though the chemicals are closely related. But more egregiously, Klonopin is DEFINITELY not a barbiturate, it's a benzodiazepine, like Xanax or Valium. Heroin is neither a barbiturate nor a benzodiazepine, it's an opioid.

  5. lee
    February 21, 2013 #

    The students that they studied on do they even smoke weed first of all and if they do how long have they smoke i know more people have been in accident sober then on marijuana so you need to do this study over

  6. jimbob
    February 21, 2013 #

    These bs "studies" are the Invention of insurance companies and have been used for years to jack up prices. The "study" used to cite workplace issues with pot smokers, is well known to have been a copy of an alcoholism study, with the word alcohol replaced by marijuana, to show how people who use pot miss work, cause accidents, are sick more often, and end up costing more in medical treatment, essentially forcing companies to test for pot or face higher premiums.
    This tool referencing some poll stating that 6.8% of people who were involved in accidents tested positive for THC means what? Pretty much nothing considering that this only shows that this tiny percentage of people had consumed marijuana sometime in the last Month or so.
    I'm not saying it's ok to get wasted and go out and drive. I don't do it simply for the reason that if I'm driving along and some idiot crashes into me and kills themselves, and there I am with THC in my system, I'm liable to wake up in the hospital handcuffed to my bed, being blamed for the whole thing.
    This is the same kind of BS that I'm sure has suddenly caused my pharmacy to start labeling my ADD medicine, that I've taken for years, with a new sticker stating that "taking this medication may impair your ability to drive or operate machinery". While I'm dumbfounded by this, I know better than to leave them in that bottle just for the same reason. If I'm laying there in the road, the only one alive after some horrific accident that I didn't cause, and there's this bottle in my pocket, with this BS sticker on it, I could be blamed for being "impaired".
    Sorry for the rant. The bottom line. Be careful out there. Put away the bowl, AND the cellphone, turn down the radio, make sure your windows are clear, don't drive like an idiot, and pay attention. Pot doesn't kill people, bad drivers do.

  7. Joseph
    February 21, 2013 #

    I have no concern about drivers who have smoked a little weed, I am more afraid of the 17 year old driver coming at me in the opposite lane holding a cell phone in front of their face.

    • dan
      February 21, 2013 #

      True dat.

    • lyte
      March 16, 2013 #

      Indeed! @ Joseph, oh didn't u heard? Text n is the new high out there. Awful! Indeed

  8. Anonymous
    February 22, 2013 #

    Amen! Brother Joseph!

  9. ramon gomez
    February 22, 2013 #

    wel i can only speak for myself im a soon to be 73 years old . i have been a pot smoker since i was 15 and driving while smoking pot since i was 22.i have never had an accident or had any dui.s or tickets . a couple of years ago i got a notice from my insurance co.congragulating me for 50 yrs of safe driving. for a 8 year period i had to drive through a windy part of my journey 75 miles one way through 1 stretch that was windy as hell sometimes it would push my car abit on to another lane . it was scary but i always made it if i smoked a joint for my 75 mile journey home i was always more relaxed and alert no trouble . if i drove those same 75 miles home straight without any pot i would sometimes get sleepy after about thirty or forty miles after working all day sometimes working over time and working double shifts i have been retired now for 11 years and i still smoke my pot but dont drive as much but i honestly believe that if it wernt for pot keeping me awake and alert i would probebly wind up being a statistic. on the road i dont recomend it for anyone to drive and smoke pot but it worked for me i have a perfect driving record to prove it

  10. Angela
    February 22, 2013 #

    Wow, many of you sound the same as the idiots that say " I can have a drink or two and drive no problem", and then proceed to kill a family on the road. Look, I used to be a huge pothead in my youth, and even then, I was not ignorant enough to think it in no way affected my ability to drive. It's science people, mood/brain altering substances alter EVERYTHING you do. Driving doesn't get a magical pass just because you want it to. Yes, regular smokers are affected less just like regular drinkers are affected less, but the law is for EVERYONE because the majority of people are impaired A LOT MORE than they realize by substances. By the way, you people making these ridiculous claims that you are somehow above the science of substances and brain chemistry are the EXACT Reason that pot is still not 100% legal. You sound like idiots by disputing facts, if you actually admit the downsides to pot and work to make it realistically lawfully legal, you just might actually get it legalized!

    • juan
      February 23, 2013 #

      There are no facts being disputed; the goverment and corporations have lied about weed from day 1 of this issue. You only believe it dangerous because you were told it is dangerous. Being high is not like being drunk or taking acid, and it does not alter the mind. Just believing something you were told does not make it a fact. You people just want to sound smart, and you dont care about the several hundred thousands of teens and young adults who have had their opportunities and freedoms stole from them over propaganda like this while our government continues to be run by true criminals. And you cant understand why people under 26 hate republicans!? Lmao

    • Ben
      February 28, 2013 #

      …and you have apparently have not been keeping up with the news on legalization or why it hasn't happened. Also marijuana is not illegal because of how it effects you, it's illegal because of A) racism against Mexicans. During the depression they needed a way to deport them and they brought the custom of smoking weed across the border, so they found it a good way to send them back. And B) because of Harry Anslinger who just didn't like weed and went on a Nazi propaganda campaign smearing the use of marijuana with movies such as Reefer Madness that contain nothing but lies but swayed popular opinion with their scare tactics. If marijuana was actually illegal because of what you are saying, I might actually listen to your BS.

      • Juan
        March 21, 2013 #

        I already know that. It also threatened many established industries. But today it is just money. What I was saying is they have used fear and misinformation to justify oppressing people. I don't understand your argument because you are agreeing with me.

  11. joebanana
    February 23, 2013 #

    6.8% were stoned, how many were drunk and how many completely sober? I'll bet more were sober than stoned. Lets say 50% were drunk, add the 6.8% stoned, equals 56.8% "impaired". That would leave 43.2% sober. So, What I take away from this is, sober drivers are 43.2% more dangerous than stoned drivers. Huh?

  12. M McL
    February 23, 2013 #

    Brought to you by the Industrial Drug Testing Complex.

  13. juan
    February 23, 2013 #

    According to this poll, 93.2 % of drivers involved in accidents were not on weed.

    Logical conclusion: more people should smoke weed, and we would have less accidents.

    See, what I did there, that's what you do.

    Now, let's talk about senior citizens that shouldnt be driving…

  14. John
    February 28, 2013 #

    I drive a taxi in NYC and I smoke weed regular before and during breaks for 20 years and never had traffic accident. It's total Bs.

  15. Ben
    February 28, 2013 #

    The only car accident that I am aware of directly related to marijuana in 21 years of smoking it multiple times a day is… a buddy of mine drove through a T intersection while searching under his seat for his bag. I would like to point out that he was completely sober. That's it. I would also like to point out that in the entire history of mankind, if there was ONE SINGLE PERSON who had died of cancer directly related to pot, don't you think the government would have latched on to that person and used them as a poster child that weed is bad? The problem is, finding that one person. There isn't one. There are just a whole bunch of lies about marijuana. Don't believe the hype.

  16. JNelz
    March 1, 2013 #

    Wow…so many so defensive & saying this is all BS & lies. Pretty sure most of you smoke weed now or used to. Funny how none of you mentioned a simple YES or NO to whether or not weed actually alters the mind. Maybe that's because you know that it does alter the mind & that's what you love about it so much. I agree with Angela…maybe if you smokers admitted some of the down sides it would be easier to have a real conversation about legalizing weed.

  17. Devan
    March 1, 2013 #

    I am not a regular user, though I do partake from time to time. I will say, I play video games far far better stoned. Thus, hand eye cordination is not reduced, as such is proof. Also, I un-interuptedly obey every law of the road, which I can not say is the case while sober. I stop at every stop sign. I never speed; if anything, I am too slow. I only ever wear a seatbelt while high. I double and triple check before pulling out, and even wait at times I could have went and had minutes to spare. I have never crashed while high, but have so sober. I will say beond reasonable doubt that I am far safer behind the wheel while stoned. I am an aggressive sober driver, and a defensive stoned driver. Drinking and driving is deffinately a no-no however.

  18. cannaBUS
    March 2, 2013 #

    Great propaganda piece!!! Let's make up some more numbers and show them how many people who try pot die instantly next time. Maybe we can link pot to guns ' people smoke pot and get the gun munchies and want to kill people, that's next right?

  19. If you're 428 you get ate more
    March 3, 2013 #

    Great write-up.

    Tip for the rest of you pothead losers: "Defensive driving" doesn't mean "get defensive about your heretofore undiscovered constitutional right to drive under the influence.

    Drug addicts can rationalize ANYTHING and I'm sure you'll have as many excuses when you kill someone or cause them a lifetime of pain and suffering.

    Oh and you probably all drive drunk too. Don't lie.

    • Tony
      March 4, 2013 #

      Proof that you're losing an argument: Call your opponent a stupid pot head loser….

    • Storm Crow
      March 6, 2013 #

      I come from a family of alcoholics. CANNABlS prevents my drinking. I have already out-lived my mother and am FAR healthier than she was. I work in education, been married for 44 years to the same man, and my adult sons love and respect me. I have used CANNABlS for over 45 years. Why do I use CANNABlS? It prevents my frequent migraines that are debilitating and, in general, enhances my life!

  20. Joseph
    March 3, 2013 #

    The real elephant in the room and the one that won't be discussed, Is the fact that prescription drugs are far more dangerous To drive on but no one will talk about this Because the drug companies own this country and control the conversation.