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.

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. Mike Alan
    September 21, 2013 #

    As a pot smoker for 40 years I can tell you 100% fact driving stoned is very dangerous. In the late 1970s when one for the road was normal, driving drunk or stoned was ok. Neither is safe. Driving high kills. Driving drunk kills. Anyone who thinks they drive safe when is fooling themselves because they make this determination while under the influence of a drug. Btw, I smoke pot pretty much everyday and have done so for about almost 40 years.

    • Jack
      September 28, 2013 #

      I don't feel like I'm being dishonest at all when I say that while I've only been smoking for 20 years (length is irrelevant) I've never been in a pot related accident. No coffee is another matter. I won't ever drive if I haven't had my morning coffee. I'm not suggesting that pot doesn't impair my driving ability. It may… though I've never felt impaired and feel that a more accurate portrayal would be that smoking makes me hyper alert. I certainly won't try to speak for everyone. To do so would be foolish.

  2. 7/4jro
    September 22, 2013 #

    I smoke loud. I try my hardest to keep off the road though after smoking, for good common sense reasons. First off, to anyone who has the thought that smoking and driving is ok, grow the f*** up. It is almost like trying to say there is no awesome distracting feeling when thc enters the body. I have hit two deer when high off . (with my fists)….(jk my car) its one thing to drive high, you forget driving past people, loss of memory on what route you took, or just simple fear of trying to look like a sober driver. It's a completely different thing if music is involved. I almost HAVE to sing along if the song is great enough, if pink floyd is on I might as well be driving into your house. All you would see is me singing 'wish you were here' parked in your kitchen. It's dangerous because of how fun it can be, not as many regrets to smoking as there is drinking. Other than the jail part.. don't smoke or drink and then drive b******!

  3. Holdin
    September 24, 2013 #

    I have horrible ADHD and it is made worse by driving. If I smoke a blunt and drive an hour later, I can focus on the road and the hazards around me- ergo, making me a safer driver.

  4. Ellen Hall
    September 24, 2013 #

    Thanks, everyone, for making this such a spirited discussion — we really appreciate hearing your viewpoints. But please remember to be nice and not make personal attacks. And to keep the conversation interesting for everyone, please only add comments that offer a fresh perspective on the subject.

    • MikeHike
      October 22, 2013 #

      Ellen, I know you say be nice and listen to fresh perspectives. But when people talk about driving while being under the influence of THC, they are asking for negative and personal comments. It puts everyone at risk as it is a public road.

  5. John Thomas
    October 9, 2013 #

    British marijuana "studies" are primarily of the NIDA type. As we see here, they didn't even do their own experiments. They just twisted the statistics they found in other studies.

    Some people think marijuana consumption causes accidents like alcohol does. It doesn't, for various reasons. Research has shown marijuana is less intoxicating. More importantly, while alcohol drinkers think they are better drivers and so drive faster and more aggressively, marijuana consumers are very aware of their altered consciousness and correctly judge when they are too impaired to drive – refraining from doing so. If they must, they correctly compensate for their altered state by driving slower and more cautiously.

    The point is, judgment is not affected like it is with alcohol. Marijuana consumers simply don't put themselves or others in harm's way. Consequently, the preponderance of the research shows marijuana is NOT a significant cause of auto accidents

    Marijuana and Driving: A Review of the Scientific Evidence

    The Hartford Courant confirms this:

    >>>"States that legalized the medical use of marijuana have had a drop in deadly automobile crashes, suggesting that some people who would otherwise drive drunk and kill someone are smoking weed instead, according to research by three economists."

    • ThinkOutsideTheFox
      October 17, 2013 #

      John Thomas, you nailed it. The flaw in the authors argument and that of the otherwise uninformed, is quite simple. Notice this statement; "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." Yes that is quite true of alcohol and probably a lot of other drugs including caffine. Marijuana on the other hand, makes one more aware of any impairment, and results in a more careful, almost parinoid to make mistakes, type of driver, as opposed to an overconfident, aggressive driver. Yes, they are slightly impared, but they know it and tend to be more careful. Their reaction time may be a tad slower, but they will give themselves more room, and are much less likely to speed or tailgate, or otherwise be aggressive in their driving, etc.

  6. BJ Allen
    October 11, 2013 #

    Any substance which alters the conscious state should not be used if one needs/plans to operate a motor vehicle. The arguments regarding such are moot. Don't do either and drive….if you don't care about injuring or possibly killing yourself, that's fine. But do think about the innocent people traveling in other vehicles or walking on or along the same roadway where you are driving while impaired.

  7. Zack
    October 12, 2013 #

    Wow people really are clueless im a much safer driver stoned…sober you might find me passing on the shoulder at 100+ stoned no way im in the slow lane doing 55 not that im impaired and have to compensate rather you are just chilled out and dont feel all tense and rushed on the road

  8. Hank
    October 15, 2013 #

    I'm walking from now on, your all crazy:….

  9. PinkTyler
    October 18, 2013 #

    You are in serious denial!!! Hahahahahahah!! OMG. Those who deny having impaired judgment while high on THC are flat out lying. Seriously. If the hight didn't impair you, it wouldn't be worth doing. I smoked pot a lot when I was young and thought I knew everything. Then I grew up. Smoking isn't healthy…period. NO type of smoking is healthy. Putting smoke into your lungs intentionally isn't a very bright thing to do…it may be your right to be able to do it, but that doesn't make it a smart thing to do. The only people who believe there is nothing wrong with smoking marijuana are those who smoke marijuana. Personally, I don't care if people smoke it. It isn't worth all the tax money we use to try and stop it, but to say it is safe and better than alcohol or anything resembling those remarks is sheer idiocy.

  10. PinkTyler
    October 18, 2013 #

    Not being in a pot related accident doesn't mean you aren't impaired and doesn't mean you should be driving. It merely means you have been lucky

    • James Scholl
      October 21, 2013 #

      Not being in a sober related accident doesn't mean you are a good driver and it doesn't mean you should be driving. It merely means you have been lucky.

  11. David
    October 21, 2013 #

    " 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)."

    Yeah and what were their BACs??? You can have a drink or two or take a couple tokes and drive fine but if you put them together? Watch out. I myself can have a couple of beers and be fine but take a couple tokes afterwards? I can find myself staggering!

    Stick to cannabis…It's much better for you… In multiple ways… Physically, mentally and spiritually…

  12. Dewewantto
    October 22, 2013 #

    Why can I play my Race Car 3 game Better and Safer when I'm stone?

  13. smartypants
    October 24, 2013 #

    Driving under the influence of drugs and/or alcohol is a childish mistake. grow up, don't drive after recreational intoxication . period! That is all