Driving & Cannabis

Studies have indicated that the use of THC cannabis while driving impacts your:

  • Reaction time
  • Visual function
  • Concentration
  • Divided attention
  • Following distance
  • Speed

THC cannabis can impair judgment and performance in a naïve patient. It also compromises your ability to handle unexpected events, such as a pedestrian darting out on the roadway and doubles your risk of a collision.

Therefore, driving, operating heavy machinery, or safety-sensitive activity should be avoided if possible. If using cannabis daily, THC tolerance may develop and there may be minimal impairment (similar to tolerance to opioids). However, this does not mean it is safe to drive. You should not drive until you become accustomed to the effect of cannabis. The acute effects of inhaled cannabis subside generally after about 3 hours.

Avoid driving, operating machinery important decisions, or activity alike for at least:

  • 4 hours after inhalation
  • 6 hours after ingestion of oils or edibles
  • 8 hours after any feeling of euphoria
  • longer than 8 hours if feeling intoxicated

BOTTOM LINE: If you feel impaired, you should not drive.

Many argue that if the CBD content and the THC content are equal, they cancel out and you won’t have any side effects. However, there are no studies to suggest this is true when it comes to driving. However, taking only CBD cannabis, will give you no psychoactive effects and may be an option for circumstances requiring high cognitive function.

Although the weight of evidence reveals significant psychomotor impairment as a result of THC cannabis use, it is difficult to predict the extent to which a given amount of cannabis will have on a particular individual.

Patients must use their judgment when using cannabis, narcotics, muscle relaxants, alcohol, or any other substance which can reduce cognitive abilities.

There are no specific laws or roadside testing procedures for cannabis. However, if you are pulled over, a police officer may make a demand for you to do a Standard Field Sobriety Test (SFST). An SFST test is typically administered roadside and consists of a police officer putting a suspected impaired driver through a series of standardized sobriety tests.

For more information, go to http://www.rcmp-grc.gc.ca/en/cannabis

Drivers who are impaired by drugs are subject to the same penalties as those impaired by alcohol. By using cannabis safely and consciously, you are protecting your life as well as the lives of those around you!

Check your Provincial/Territorial laws to determine what administrative penalties may be imposed upon you, in addition to any criminal penalties, for impaired driving where you live.

Medical Cannabis, Safety-Sensitive Occupations & Driving Privileges

Health Canada has stated that “using cannabis or any cannabis product can impair your concentration, your ability to think and make decisions, and your reaction time and coordination. This can affect your motor skills, including your ability to drive. It can also increase anxiety and cause panic attacks, and in some cases cause paranoia and hallucinations.” (http://www.hc-sc.gc.ca/dhp-mps/marihuana/info/cons-eng.php)

“Although no studies have been carried out to date examining the effects of cannabis or psychoactive cannabinoid exposure on psychomotor performance in individuals using these substances solely for medical purposes, it is well known that exposure to such substances impairs psychomotor performance and patients must be warned not to drive or operate complex machinery after smoking or eating cannabis or consuming psychoactive cannabinoid medications (e.g. dronabinol, nabilone, nabiximols).” (http://www.hc-sc.gc.ca/dhp-mps/marihuana/med/infoprof-eng.php#chp771)

More information is available in the following document published by the Canadian Centre for Occupational Health and Safety to help guide employers in managing employees using medical cannabis:  Workplace Strategies: Risk of Impairment from Cannabis


Government of Canada




Canadian Public Health Association

Canadian Centre on Substance Use and Addiction

Canada Drives