Marijuana Use and Driving
marijuana use and driving

Marijuana Use and Driving

As more states pass laws to legalize marijuana, many are unsure of the safety of marijuana use and driving. No level of marijuana use is acceptable for young drivers, even in states where it is legal. It is illegal and unsafe for teens to drive high, just like it is illegal and unsafe to drink and drive. A DUI is given to anyone who is suspected of driving under the influence of drugs or alcohol and can negatively impact your teen’s future.

In 2018, 27% of all adolescent DUIs in Colorado involved marijuana. A police officer can stop anyone suspected of driving with marijuana in their system. A DUI citation can result in expulsion from school and loss of college scholarships and grants.

While the legal age for using retail marijuana is 21 and for using medical marijuana is 18 in some states, it’s never okay to drive while impaired. Although the limited body of work exploring the impact of THC (tetrahydrocannabinol, the active ingredient in marijuana) on driving is mixed, generally accepted results report a two-fold risk of a motor vehicle crash among drivers with any THC in the bloodstream.

Detecting clinically significant levels of THC in the body can be complicated, however. Urine levels, which in many states are equated to blood levels (and are both illegal), can reflect past use and may not reliably detect people who are actually driving high. An accurate roadside test for drug levels in the body doesn’t yet exist.

How Marijuana Use Affects Driving

While laboratory studies of people with THC in their bloodstream do not support significant impairment on single tasks, such as memory, addition, or subtraction, there may be more significant impact on multitasking and handling unexpected events (which are critical components of safe driving):

  • Marijuana can slow reaction time and the ability to make decisions.
  • Marijuana can impair coordination, distort perception, and lead to memory loss and difficulty in problem-solving.
  • Marijuana use can have long-term effects for teens and young adults on brain development. Neurodevelopment continues until at least the early or mid-20s, and marijuana use impacts how connections are formed within the brain.

The risk of impaired driving associated with marijuana in combination with alcohol appears to be greater than that for either by itself. Some researchers suggest that resources are better directed toward reducing drinking and driving or reducing the mixing of alcohol and marijuana while driving.

Click here for tips on talking to your teen about impaired driving, including driving high.

Click here for information on impaired driving laws.


After alcohol, marijuana is the drug most often linked to drugged driving.

More Marijuana Use and Driving Facts and Statistics

  • Local enforcement agencies in CO and WA states report marijuana impaired driving as somewhat or very common.

  • Car crashes have increased by as much as 6 percent in CO, NV, OR, and WA as compared with neighboring states that have not legalized marijuana for recreational use.

  • Marijuana, like alcohol, negatively affects a number of skills required for safe driving, including coordination, memory, and judgment.

Pick Your Practice

With a couple of clicks, think about what skills you would like to practice first as a learner driver, and we’ll point you to videos and tips on how to practice them. Take this online driving quiz to Pick Your Practice!

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