How Marijuana Legalization Has Affected Driving

How has driving changed in the states that have legalized marijuana?

marijuana legalization crowds

As of November 9, 2016, there are 28 states and the District of Columbia that have legalized marijuana in some form; seven states (Alaska, California, Colorado, Massachusetts, Nevada, Oregon, and Washington) and the District of Columbia have legalized marijuana recreationally.

It’s now been four years since Colorado and Washington got the ball rolling nationally, which makes us wonder about the impact an increased (legal) use of pot might have on road safety. Has marijuana legalization led to reckless driving? Have fatalities gone up? And just how different is marijuana from alcohol in terms of driving?

The Process of Marijuana Legalization

Colorado, Washington, Oregon, Alaska and the District of Columbia have all legalized marijuana in some way but their laws are in no way the same. After this legalization, some may conjure up an image of hippies sitting around in a circle, beating on bongos and smoking their precious Mary Jane but in reality these states’ marijuana laws are quite strict. Each state has different legalities. In Colorado, for example, you can grow up to 6 marijuana plants, but in Washington you are not allowed to grow any plants at all. So while some might assume that these states all carry the same laws regarding marijuana, it is important to note that their differences are quite salient:






These intricate and differing rules governing recreational marijuana can be confusing—but because these laws are so new, and only at the state level, it is hard to have any sort of standardization.

Marijuana impacts your senses, causing impaired judgement and slower reaction time.

Mary Jane on The Road

The legalization of marijuana leads to a lot of concerns regarding “drugged driving”–what happens when people get behind the wheel with marijuana in their system? Ever since marijuana has been legalized, prohibition supporters and Smart Approaches to Marijuana (SAM), an anti-marijuana legalization group, have stated that more drivers are being found with marijuana in their system. They have even gone to point out studies showing that there is an increase in the number of drivers testing positive for marijuana who have been involved in a fatal car crash.

The problems with these studies are that this “increase in the number of drivers testing positive” could just have to do with the fact that more people are smoking pot in general. You would expect for the number of pot smokers to increase with legalized marijuana laws and with the overall population smoking more marijuana it is easy to understand why more of the driver population is smoking marijuana as well. So, it is hard to say whether or not the use of marijuana is actually contributing to these crashes.

marijuana legalization signs

Also when looking at the car fatalities from 2011-2013 in Colorado and Washington we have seen that total fatalities have gone down. In Colorado, fatalities jumped from 2011 to 2012 but then dropped again in 2013. And in Washington, fatalities have been gradually decreasing since 2011. Of course these continuing drops in roadway fatalities could be due to some other factors like better built cars or improved infrastructure. But if these states were seeing higher fatalities than before legalization, there’s no doubt that prohibition supporters and SAM might blame the increase on legalized marijuana.

Another problem is that these states are attempting to compare “marijuana-impaired driving” with drunk driving. The Colorado Department of Transportation has stated on their website that there is a legal limit for marijuana impairment while driving:

“Colorado law specifies that drivers with five nanograms of active tetrahydrocannabinol (THC) in their whole blood can be prosecuted for driving under the influence (DUI). However, no matter the level of THC, law enforcement officers base arrests on observed impairment.”

However, this legal limit of five nanograms does not tell us whether a person is impaired or fit to drive. Marijuana is completely different from alcohol so it is hard to act as if they are similar. A marijuana high usually occurs within 30 minutes of the initial consumption and can last for about three hours. However, depending on the person–every individual metabolizes marijuana differently–traces of THC (marijuana’s primary active ingredient) can stay within the body for a few days or even weeks.

The National Highway Traffic Safety Administration (NHTSA) has released a new study reporting that marijuana does not significantly elevate the crash risk of a driver. The results showed that drivers with alcohol in their systems were 12 times more likely to get into a crash whereas drivers with THC in their system had only a 5 percent more chance of crashing than a sober driver. “Marijuana is complicated. This study is a very important part of beginning to learn the factors we need to pay attention to,” Gordon Trowbridge, communications director at the NHTSA says. “We know far less about marijuana at this point than we do about alcohol”.

Take Aways of Marijuana Legalization

With such vast differences between marijuana and alcohol, it is hard to treat them the same. What we need now are better roadside mechanisms–like breathalyzers for alcohol–for detecting marijuana-related impairment. A few companies are already developing pot breathalyzers that might be able to help law enforcement detect whether someone with THC in their system is actually impaired at the time.

Nonetheless, marijuana does impact the driver’s senses, causing slower reaction times as well as impairing judgement, so no matter what, impaired drivers should never get behind the wheel.

  • Ed Wood

    It is not true that NHTSA reports that marijuana does not significantly increase crash risk. Not finding a significant link is not the same as finding there is not significant link, particularly with a study that was not designed to find such a link in the first place.

    Colorado reports no increase in DUID citations since commercialization of pot simply because it does not issue any DUID citations. Only DUI citations, which do not differentiate between alcohol and drugs. If you don’t measure something, you’ll remain ignorant about its prevalence and consequences.

    • Duncan20903

      Things change. The Colorado State Patrol started counting in 2014. The CSP reports arresting 354 people for cannabis addled driving and 320 people with both cannabis and any other drug which was all but exclusively drinking alcohol. CSP reports that they made a total of 5,546 arrests for impaired driving in 2014.

      • Ed Wood

        Thanks Duncan. That’s correct. And CSP issues roughly 20% of the DUI citations in the state. In addition, the City of Denver, City of Lakewood and Larimer County also track DUID, each using a system of their own – but nothing is collated statewide, there are inconsistencies in data collection criteria from one agency to another, and none of them are able to track judicial outcomes.

        • Duncan20903

          How long will it take you to figure out that the problem is driving impaired for any reason? Are you really so thick that you think that if you can stop a scofflaw from driving when cannabis addled that would result in a driver sober as the proverbial judge?

          Why is it that you don’t believe in personal responsibility? Choosing to enjoy cannabis does not inevitably produce an impaired driver. Nobody is lobbying for the repeal of laws against impaired driving. Nobody.

  • Michele Dardis

    you might want to read the paragraph Mary Jane on the road. you got a repeated word in there. Last Sentence the word “Have” shows up twice. :)

    • Josh Waldrum

      Thanks Michele! We’ve updated the error in the post.

  • Oscura Diosa

    Allow people to grow their own charge for the seeds maybe but it is stupid to force you to buy a weed that can grow anywhere from a supplier.