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Drugs & Health Blog

Legal Marijuana and Driving: A Public Safety Problem

This blog post is archived and is no longer being updated. For the latest content, please visit the main Drugs & Health Blog page.
Sara Bellum

When you’re driving down the highway at 60 miles per hour, you need a clear head. Driving while distracted by your phone or driving under the influence of alcohol both can lead to crashes and tragedy. Driving under the influence of marijuana is also dangerous, because of the way the drug affects the brain and body.

Recent news reports have talked about how drugged driving crashes and deaths have surged since medical marijuana has become legal in more states. Now that marijuana is legal for those over age 21 in Colorado and Washington, the rates of drugged driving are likely to increase even more.

This poses a problem for police and our criminal courts because there isn’t yet a test that can show a person’s marijuana levels the way a “breathalyzer” test can show how much alcohol is in a person’s system in just a few seconds. It also poses a problem for public safety. When people drive after using marijuana, they put themselves, their passengers, and anyone else on the road in danger.

Evidence from driving studies indicates that marijuana can harm a driver’s ability to pay attention, awareness of time and speed, and ability to draw on information gained from past experiences. Impairment increases a lot when marijuana is combined with alcohol.

Another problem is that marijuana stays in your system a lot longer than alcohol, which leaves a few hours after you stop drinking. A recent NIDA-funded study looked at long-term marijuana users very closely. The researchers found that even if a person hasn’t used marijuana in a month, it could still be detected in their blood—which may have an effect on a person’s ability to drive safely.

The bottom line: Use of any mind-altering drug makes it highly unsafe to drive a car and is against the law—just like driving after drinking alcohol.

Comments posted to the Drugs & Health Blog are from the general public and may contain inaccurate information. They do not represent the views of NIDA or any other federal government entity.


Excuse me????? Are they suggesting if you smoke once in a while that youre unable to drive for up to a month b/c it still shows trace amounts in your blood ??? this is the silliest claim I've ever heard... Oh, and while I was typing this, there was prob 5 deaths due to Drinking/driving somewhere in this country.. and 0 related to weed... Unreal the people who write this garbage are pulling thoughts out of the sky... do some research before making silly claims !
You should do some research first before criticizing the National Institute of Drug Abuse (NIDA). Read the article they provided to make informed comments!
Truth is that many of these marijuana legalization proponents use the same kind of research that sellers of scam medical devices do. Junk science, used to confuse vulnerable individuals.
either way it go you just might die because u smoked they just mean that I do's not make things better when u are fried and your going 90 miles a hour in a car trust I have been there and I almost died
I'm in favour of a ban for the period that drugs can be found in the body, Go to a proper rehab, (narconon comes to mind) do a proper detox and get all the drug residues out of the system and then be allowed to drive again, the alternative is Russian Roulette with other drives, countless deaths and maimings and all because some individuals can't take responsibility for their own lives.
I think that you can do drugs but only if its right they should still have a buddy to drive them home just like drunk drivers.This was stupid the thoughts were messed up i mean more people die of drinking then smoking i just hope who ever did this crap will really take his time and look up the right stuff to say
For me at the end of the day if you decide to use drugs and drive you need to think beyond yourself. I wouldn't want to be the first to kill someone smoking weed. When in doubt don't drive while choosing to smoke weed. Keep safe.
what about the people who are popping 10 different pills so they can drive.just beacuse someone smoke it doesnt mean they cant drive

You're right.  Abusing over-the-counter and/or prescription drugs when driving is very dangerous.  In fact, use of any mind-altering drug makes it highly unsafe to drive a car and is illegal.  Drugged driving puts everyone on the road at risk.  

Weedy's dead wrong, an increasing # of people are dying due to THC impaired drivers. Just ask this driver: “[Joseph Beer, 19,] may have been looking to go on a joyride that night, but all he caused was despair for the families of the four teens he killed by choosing to speed down a public parkway after smoking marijuana.” DA Kathleen Rice
Sorry, but the research does not back up the idea that the presence of cannabis metabolites equals intoxication. Also testing done in other countries does not back up the conclusions of the studies done here that say cannabis is to blame for car wrecks. One must control for other factors; that makes the evaluation of car wreck rates a bad way to do studies on the effects of cannabis use on any ability since effects vary so much from person to person. Also other studies done on cannabis use have not controlled for other major socioeconomic factors that influence the outcomes and conclusions of the studies, therefore the conclusions are in error. To depend on one study for a range of other studies outcomes is just plain bad science. Proper peer review seeks out and includes positions different from one's own. [link removed, per comment guidelines]
Actually... the rate of crashes due to pot in the system has gone down since legalization in Colorado. So has the crime rate. It would be nice if you would mention actual FACTS instead of just "well this might happen. lets scare the kids"

Actually, Aaraon Sanders, marijuana contributed to 12% of traffic deaths in 2010, more than triple from 2000.  Colorado, specifically, has seen a significant increase since medical marijuana dispensaries were legalized in 2009.  We're not trying to scare kids, but it is important that everyone understands the risks of drugged driving.  Those are the facts.

Please describe how use directly contributed. Or was it (should have been) deemed "associated"? There is a big difference there. It would be great to see the data on these claims to agree or disagree with your statement. Please cite your information. Thank you.