Risks of Driving Under the Influence of Cannabis

As with alcohol, drivers must not get behind the wheel if they have used cannabis because its effects on the brain can impair their ability to drive.

The effects of cannabis vary according to a number of factors and can last for several hours after consumption. Cannabis severely affects our perceptual and psychomotor functions, which are essential for driving. For example, drivers whose faculties are impaired due to cannabis may have:

  • Difficulty concentrating and staying focused on the road environment (e.g., failing to obey road signs)
  • Longer reaction times and slower reflexes (e.g., taking longer to brake)
  • A reduced ability to properly assess their surroundings
  • Difficulty maintaining a straight course
  • Coordination problems
  • Impaired judgement

People who drive under the influence of cannabis are almost twice as likely to have an accident as those who have not used the drug. Drivers who consume alcohol and cannabis together have a much higher risk of causing an accident.

To learn more about the risks of cannabis use and driving, visit the Société de l’assurance automobile du Québec (SAAQ) website.


DOUVILLE, Marisa et Pierre-André DUBE. Les effets du cannabis sur la conduite automobile. Institut national de santé publique du Québec, 2015, 34 p. (in French only)

ROGEBERG, Ole et Rune ELVIK. The effects of cannabis intoxication on motor vehicle collision revisited and revised. Addiction, vol. 111, no 8, 2016, p. 1348-1359.

Last update: March 30, 2023 11:12 AM