Marijuana Use and Driving

What’s the Problem?

Driving when you are under the influence of marijuana may be dangerous, just like driving drunk. Driving is a complex task and requires an alert and responsive driver. Marijuana slows down reaction times and increases lane weaving.^1-3

Who’s at Risk?

People who combine marijuana with alcohol are particularly at risk. The risk of driving impaired, and the risk of being in a fatal crash, appears to be greater when marijuana is combined with alcohol compared to when either substance is used alone.^1-4

Can It Be Prevented?

The good news is that driving under the influence of alcohol or marijuana is preventable. See the following steps you can take:

• Designate a driver when with a group before drinking or using marijuana.
• Don’t let your friends drive impaired and never ride with an impaired driver.
• Get a ride home, call a taxi, or rideshare service if you have been drinking or using marijuana.

The Bottom Line

Driving while impaired by any substance, including marijuana, is dangerous to the driver, their passengers, and others on the road—but it can be prevented.

Case Example

1. Ashley got a ride with Cara to Staci’s house where they decided to hang out for the night. They stayed out much later than planned and Cara fell asleep on the couch after having a joint and a beer. Two hours later they’re finally ready to go home. Ashley knows that Cara’s been drinking and using marijuana, so she is concerned about Cara driving them home. Cara suggests they spend the night to be safe.
2. About five hours ago, Jordan, a 32-year-old dad, ate some marijuana gummy bears. At first, he didn’t feel the effects so he thought “doubling up” the dosage might do the trick. Now he’s feeling dizzy and off-balance, and he just remembered he needs to pick up his son from school today. He doesn’t have far to drive. It’s 3 p.m. and the streets are full of kids walking home and there is busy daytime traffic. Instead of driving, Jordan calls his sister who agrees to pick up his son.

References

1. Lenné MG, Dietze PM, Triggs TJ, Walmsley S, Murphy B, Redman JR. The effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand. Accid Anal Prev. 2010;42(3):859-866. doi:10.1016/j.aap.2009.04.021.
2. Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013;59(3):478-492. doi:10.1373/clinchem.2012.194381.
3. Hartman RL, Brown TL, Milavetz G, et al. Cannabis effects on driving lateral control with and without alcohol. Drug Alcohol Depend. 2015;154:25-37. doi:10.1016/j. drugalcdep.2015.06.015.
4. Centers for Disease Control and Prevention. Teen Driving Facts [Online]. (2017). National Center for Injury Prevention and Control, Centers for Disease Control and Prevention (producer). [Cited 2017 August].