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. Avatar for Jessica Guerin
    January 11, 2013 #

    Well DUH !! Of course it will impair you ability to drive. Actually I would much rather have a pot smoker than a drunk on the road as it does not impair your brain to the extent that alcohol will. A recent study showed that states that legalized maraijauna for medical use had about a 50% reduction in fatalities

    • Avatar for Jessica Guerin
      Donna Casey
      February 9, 2013 #

      Of course it impairs your driving. So does Nyquil or any prescribed drug or not sleeping for several days or alcohol or anger.

      Most pot smokers don't want to drive when they smoke… as is often said, "I'll BUY, if YOU FLY!"

  2. Avatar for Jessica Guerin
    January 31, 2013 #

    sounds like a lot of denial to me. smokers say smokin's ok. drinkers say drinking's ok. etc. I've read all the posts and the best thing is the spelling errors. the rest is just opinion. IMHO. DON'T DO ANYTHING AND DRIVE AT THE SAME TIME! it's ok to kill your own stupid self, BUT, think about the van full of a family that's taken out by a person impared by drugs. (yes, alcohol is also a drug, DUH!)

  3. Avatar for Jessica Guerin
    January 31, 2013 #

    Seems pretty reasonable to me. Double the risk? Not good news, but not so bad. If I drive to the store, I probably won't crash. If I do it twice, well, pretty similar. Not horrible odds, but you can't tell me it doesn't affect you. Yeah, if there's one thing you can do, it's land a spaceship when you're stoned. Right.

    This isn't enough to freak out about, but yeah, it confirms what we know. It's really dumb to say that pot doesn't increase your chances of a crash. ANYTHING besides total sobriety, is not good for your driving. So drive sober. Don't be a dumbass.

  4. Avatar for Jessica Guerin
    February 2, 2013 #

    you realize this is a corporate blog, right?

    • Avatar for Jessica Guerin
      February 5, 2013 #

      People don't understand what media bias is. They *think* they understand the general concept, but also think that their own government is the 1 in all of human history that doesn't brainwash it's citizens. "Someone told me weed makes you retarded, so of course you shouldn't drive like that". Well, I guess since all their other lies about weed making you homicidal/suicidal/unable to reason got destroyed by facts, now they have to convince people that legalization would mean a bunch more (as if they're aren't lots already) stoned drivers out there. never mind all the people who legally drink at Ruby Tuesdays and then proceed to get in their car and drive home "because I've only had two beers". Nevermind the studies saying that 2 beers, sleep deprivation, and even post-meal tiredness can greatly increase the chances of a wreck happening. Yep, but those people don't have to go to jail or pay unconstitutional fines or anything until and unless they ACTUALLY hurt someone or damage something.

  5. Avatar for Jessica Guerin
    John Michael griffin
    February 3, 2013 #

    Lady, you have absolutely no idea what you are talking about. I'm really not trying to be a butt, but these statistics are very biased. The studies didn't show how many of the people that tested positive for THC also tested positive for alcohol. Another point that I might add, marijuana really does not change your reaction time nor change perception. You are just basing your "facts" off of somebody else's research. Don't believe everything you read and hear. Maybe you should do a little field study. I just typed this whole thing while being incredibly stoned on some high THC marijuana and everything seems pretty legible. You are a good writer and all, but don't put marijuana in a category with other controlled substances.

    • Avatar for Jessica Guerin
      February 7, 2013 #

      Wow. WOW.

      Stop smoking weed for a few months, smoke it again. And THEN come talk to us. You smoke too much or what you're using is CRAP. Your comment is ridiculous.

      TOLERANCE buddy. PUT THE PIPE DOWN and maybe you can remember what it feels like again to be a sober person that actually gets the "high" reaction from weed. Many many things can happen to people after smoking marijuna, DEFINITELY including change in reaction time and perception. Just because you have a tolerance doesn't mean the rest of the world does.

      No tolerance is TOTALLY known for a completely different view of weed that even used-to-be-stoners won't mess with.


  6. Avatar for Jessica Guerin
    February 3, 2013 #

    I was a teenager in BC Canada in the 80's and smoked a fair amount of a weed we called "BC Bud". That was some powerful pot and let me tell you I drove on it once and swore never to drive impaired again (and haven't). If forced to choose I would drive drunk any day; high on weed I kept fixating on the speedometer and forgetting to look at the road.

    This is why I have a hard time understanding those who say they can drive just fine on it. Is weed weaker now than it was then? When I got high back then I got HIGH, absolutely wasted; there was no higher brain functioning going on at all! If we had legal weed (and I'm not an advocate fyi) we would at least know everyone was smoking the same thing and would know what kind of high they were on; as it stands there is a lot of variance between what you'll find in one joint (outdated word I'm sure!) to the next and there are often other drugs mixed in.

    The fact is, when you get behind the wheel, you should be free and clear of mind altering substances. Period. And don't tell me weed isn't mind altering – that's the whole point of smoking it!

  7. Avatar for Jessica Guerin
    February 4, 2013 #

    three accidents in my life two before i was 18 and one later from driving drunk. none other than that. i never leave the house until i smoke weed.
    i also operate heavy machinery far better stoned.

  8. Avatar for Jessica Guerin
    Lorain Ohio
    February 5, 2013 #

    The intersection of Route 113 and Lake Road. A grandmother and grandaughter are sitting at a light in front of the Coca Cola distribution center. A boy who has not been drinking or using any other drugs but weed hits them from behind at a high speed. The car that was hit from behind bursts into flames, and the folks in it both burn to death. That was enough to convince me.

  9. Avatar for Jessica Guerin
    February 7, 2013 #

    ok stoners. get over it. it's just weed. smoke it on your own time and stop trying to stand for something that's your own business and no one elses.

    most people are horrible drivers. drunk. stoned. sober. weed can definitely influence anyone to do a lot of stupid things, if their tolerance is low enough. there's no point in the every-day users trying to give their defense to this article.

    we all know there are some professional "weed makes me a better person!" people out there, (and there are the people that marijuana helps for actual medical reasons )… and we KNOW it has a fan club.

    It's weed. Smoke it and enjoy your life without having to prove any study wrong just to justify your choice of a daily substance. Just because you're at the point where you can smoke weed EVERYDAY and you feel "better" about yourself or life, doesn't mean there aren't still the other users that DON'T live the "high" life permastoned, that actually still get the multiple other reactions you USED to get when you first started. No one cares how much weed you smoke everyday! And obviously there are numerous reactions that could totally range to effecting how someone handles anything, let alone a moving vehicle.

    It's so funny to me how so many stoners will go on and on announcing how great they are with weed. AWESOME It's not like you're going to stop and figure out how great you are without it anyway!

    Jeez. Weed doesn't need a parade. Focus on your other favorites so you'll have at least enough of your memory left when you're old to look back on things and remember them You'll have nothing else to do at that point but smoke anyways.

    Lifes too short to escape yourself too much. <3

  10. Avatar for Jessica Guerin
    Melvin Logan
    February 7, 2013 #

    This is a topic that many people have valid points about but some specifics have been left out. For 7 years I commuted home from work stoned without any accidents. I have had accidents when people either rear-ended me when I was waiting at a red light or they changed lanes too fast & misjudged their braking time. There are many variables to be considered. Were accidents caused by strains like Indica that cause drowsiness or Sativa that keeps one more awake. My personal experience is that I am more cautious and involved in my driving experience without being distracted. I am more relaxed than when I am strait. I have had an accident when my anxiety levels where elevated and I was straight.. Pot works for me. For others it may not apply since some of my friends are uncomfortable and paranoid on pot. It is the best pain reliever for me because I do not focus on the pain even though I may feel it . That gives me relief . I have had doctors say too bad you need to smoke a weed to get high. That shows a real lack of information since it is available as drops, food, and even a non-high form. Be careful about misinformation. If someone smokes it despite some over zealous comment by anti-marijuana groups comments they may think it is not as bad as they were led to believe. And think they were misled about more dangerous drugs and start experimenting.

  11. Avatar for Jessica Guerin
    February 8, 2013 #

    This is garbage & isn't even worth the time reading there were no facts

    • Avatar for Jessica Guerin
      March 29, 2013 #

      No facts? Perhaps if you weren't impaired by pot, your would have been able to read the bottom line which provided a direct link to the actual study:

      • Avatar for Jessica Guerin
        March 30, 2013 #

        @Daisy: Perhaps if you weren't impaired by your own prejudices, you would have been able to discern the flaws inherent to the aforementioned study and its presentation in the article

  12. Avatar for Jessica Guerin
    February 8, 2013 #

    It is really convenient that they left out three studies.One they said was a duplicate.The other two were the simulator test and the closed road test that were done on stoned drivers by the National Highway Traffic Safety Administration.They called these studies irrelevant because they showed that stoned drivers posed very limited risk while driving.The drivers were more likely to get rear ended while waiting for the stop sign to turn green.These studies also showed that the drivers drove a little bit slower and followed a little bit further back from the car in front of them.I wonder why these studies were considered irrelevant?

    • Avatar for Jessica Guerin
      February 17, 2013 #

      LMAO! "Burny" nice one!

    • Avatar for Jessica Guerin
      March 2, 2013 #

      Because like the rest of our system, it doesn't fit their agenda. How about the fact that in their own study they admit the accidents drivers only had pot in their system, not that they were intoxicated. Thc stays in the system on average of 30-50 days. Most these drivers were not currently under the influence, if they were, they probably wouldn't have wrecked. In colorado 60% of the adult population admits to smoking pot, yet no one has ever died from driving stoned, name ONE?

      • Avatar for Jessica Guerin
        March 29, 2013 #

        How in God's name do you know if no one in Colorado has ever died as a result of driving while stoned?

    • Avatar for Jessica Guerin
      March 3, 2013 #

      Are you serious? Give me a break. You've obviously never been stoned. Any stoner who is trying to refute this article is an idiot. You are NOT a better driver stoned.

      • Avatar for Jessica Guerin
        March 15, 2013 #

        You've been brainwashed by other people who were brainwashed that pot is so evil.

        Being angry and texting are two things that make you a far more dangerous driver than pot.
        70% of people admit to texting while driving. Should we ban texting and try to give DUIs to texters and road ragers?!?!

        Hypocrites just want to demonize one set of people even though far more individuals die from angry and texting drivers than from stoned ones.

      • Avatar for Jessica Guerin
        March 21, 2013 #

        Are you serious is the question?
        Your moniker is named after one of the most iconic pot smokers in movie history and you have obviously smoked only a handful of times if it all.
        I will concede that marijuana is potentially more dangerous for people who do not regularly smoke,
        but not necessarily for those of us that know what effect it is going to have on us.
        Traffic fatalities have decreased in Washington and Colorado.
        what do you think these 2 states have in common??

  13. Avatar for Jessica Guerin
    Jay Ken
    February 9, 2013 #

    I read and replied to this while driving and smoking a bowl. Now I'm home safe and sound. YOU LOSE! YOU GET NOTHING! Good day, sir.

    • Avatar for Jessica Guerin
      February 17, 2013 #


    • Avatar for Jessica Guerin
      February 21, 2013 #


    • Avatar for Jessica Guerin
      March 13, 2013 #


  14. Avatar for Jessica Guerin
    February 11, 2013 #

    These test are rigged and biased..when the truth is finally in front of your face, people like the author of this article need deported where weak minded uneducated people are sent to live out their days and they can spread their propoganda all they want. I for one have studied the stats, science for over thirty's time to treat these fakes with extreme prejudice

  15. Avatar for Jessica Guerin
    That one guy
    February 13, 2013 #

    So they had one fact – 6.8% of who were involved in accidents tested positive for marijuana.. Now what's the stat on sober people? The ONE stat they gave has no relevance

    • Avatar for Jessica Guerin
      February 22, 2013 #

      I would day that it may be more like 60% tested positive for being sober. Probably higher. How many people do you know that has wrecked. Now how many were sober. In my case maybe 90%.

  16. Avatar for Jessica Guerin
    Aaron Lee
    February 13, 2013 #

    I do believe it would come down to the individual as to if they were OK to drive while stoned. I've been smoking pot off and on, and more on now that it is legal, and I am disabled and it helps a lot with my illness, for over 20 years. Since I am a regular smoker, I am capable of driving while stoned. I did it more in college, and have taken 2 to 3 year breaks of not smoking at all, but if needed still can, even though I am usually home for good when I smoke. It's a law, and if they think I am too high to drive, they will bust me, even if I am perfectly capable of operating a vehicle while stoned, they will I would be perfectly safe because my body and brain are used to the effects, and work normally with the drug in my system. Now my wife…she never smokes. If I got her stoned and ask her to drive, she would freak out and have absolutely no business behind the wheel. She wouldn't even try. It becomes such an individual thing when it comes to how and when you use, and how much. A lot of my friends smoke from dawn till dusk, and still drive everywhere, and drive perfectly. So a regular user is more likely to drive as someone not high than a rare or occasional user would. They would tend to use data from non regular users instead of regular users since most of these tests are done with random subjects from a blind pool. Put 20 seasoned stoners behind the wheel, and they all pass with flying colors.

    • Avatar for Jessica Guerin
      J. Law
      March 6, 2013 #

      So in your mind, driving while intoxicated should be OK because alcoholics are used to alcohol being in their system and can tolerate it better than a non-alcoholic? Try telling that to the millions of people who have lost loved ones because some idiot thought they were OK to drive. Bottom line here is pot is illegal. Driving under the influence is illegal. So don't freaking do it. Your argument sir, is invalid.

      • Avatar for Jessica Guerin
        Ted Nugent
        March 20, 2013 #

        Marijuana and alcohol are two completely different substances. One major difference is that one is man-made and the other completely natural. They differ in what they do to the body in mind so that when driving is concerned, it is much harder to so drunk. That's just the way it is. No way should driving high on marijuana be illegal. Maybe not for someone smoking for their first time, but for the vast majority it should not be. As far as making you more susceptible to an accident, I disagree wholeheartedly.

      • Avatar for Jessica Guerin
        March 29, 2013 #

        J. Law, Don't ever try to reason w/a pot head. It's simply not possible.

      • Avatar for Jessica Guerin
        March 29, 2013 #

        Ethanol is the result of the fermentation of sugars or starches (both natural) by yeast (also natural). Ergo, alcohol is natural. Before humans ever figured out how to control this reaction (at least 9,000 years ago!), they likely enjoyed the intoxicating effects of ethanol produced through entirely natural, undirected processes (e.g. palm wine). Even animals drink the stuff.

  17. Avatar for Jessica Guerin
    February 13, 2013 #

    This was a letdown. All this is, is one persons opinions of the subject. Stop calling things fact if you cannot bring the proof.

  18. Avatar for Jessica Guerin
    February 13, 2013 #

    Oh, the defensiveness of the pothead – as predictable as the sunrise. Well done article, Jessica.

    • Avatar for Jessica Guerin
      George Collins
      February 14, 2013 #

      I'm a prior narcotics officer and now work in the medical profession. Upon reflection of the time spent as a cop, I realized all drugs should be legal and marijuana should be marketed as a safe alternative to alcohol.

      • Avatar for Jessica Guerin
        February 15, 2013 #

        Yeah sure you are and I'm the president of the United States…yerp -_-

      • Avatar for Jessica Guerin
        Lauren Logan
        February 16, 2013 #

        Thank you for your response it carries more weight than many of the opinions attempting to pass as information. I also have worked in the medical field and am amazed at the lack of information my the medical staff (including MDs) that are uninformed.

      • Avatar for Jessica Guerin
        Storm Crow
        March 6, 2013 #

        George, I presume you belong to LEAP. And Phil and Noah, I know of several other ex-law enforcement officers who have the same viewpoint as George! He is hardly alone in his opinion!

    • Avatar for Jessica Guerin
      February 17, 2013 #

      Vigorously and soundly defending one's beliefs demonstrate conviction and certainty. Ad hominem attacks, on the other hand, demonstrate a lack thereof. If you don't have anything smart to say, reconsider your stance. And please don't procreate.

  19. Avatar for Jessica Guerin
    February 14, 2013 #

    Glad to see Rx speed and painkillers still leading the discussion

  20. Avatar for Jessica Guerin
    Andrew Boughter
    February 16, 2013 #

    The data was skewed, the arbitrary way this was conducted did not rule out drivers under the influence of multiple substances. Also, the amount of THC to be considered impaired is dependent on the user. Heavy users may have higher levels but are unimpaired because a tolerance to cannabis develops rapidly.