Cannabis Made Clear
Cannabis and Driving: What you need to know
Driving after consuming cannabis is both dangerous and illegal. Here’s what you need to know to stay safe and within the limits of the law.
Last updated December 2, 2025 | Published on June 20, 2022
Consuming cannabis can significantly impair your ability to drive safely. In fact, cannabis consumption can double a driver’s risk of being involved in a motor vehicle crash. Impaired driving is also illegal; it’s a criminal offence in Canada that comes with serious consequences, including possible jail time.
Here’s what you need to know to stay safe.
The effects of cannabis on driving skills
Cannabis consumption affects critical driving skills in a variety of ways, including by:
- causing drowsiness
- slowing reaction time
- impairing a driver’s ability to watch and respond to multiple things at once
Studies have found that drivers impaired by cannabis have difficulty staying inside their designated lane, maintaining a steady speed and avoiding obstacles.
Cannabis affects each person differently. Depending on the individual, as well as the method of consumption and the potency of the cannabis, the effects can last up to 24 hours.
The laws on impaired driving
Penalties for driving impaired can vary, depending on
- your alcohol or drug concentration levels
- whether it is your first or a repeated offence
- whether you have caused bodily harm or death to another person
For more information, review the Government of Canada's Impaired Driving section. The law applies to all motor vehicles (including motorcycles, boats, snowmobiles and off-road vehicles), as well as driving that takes place on public and private property.
Provincial and territorial authorities also have their own legislation for impaired driving. They can impose immediate short-term licence suspensions, longer-term suspensions and bigger fines, and make offenders attend education or rehabilitation programs.
In most provinces and territories, including Ontario, there is zero tolerance for driving under the influence of cannabis for drivers aged 21 and under, novice drivers (those with a G1, G2, M1 or M2 licence) and commercial drivers.
What defines “impaired” with cannabis?
The law, however, is very clear on what constitutes impaired driving, and there are three prohibited levels for tetrahydrocannabinol (THC):
- THC levels between 2 and 5 nanograms (ng) per 1 mL of blood are considered impaired.
- THC levels of 5 ng or more per 1 mL of blood carry heavier fines and sentencing.
- Combined alcohol and THC levels are considered impaired at 50 mg or more of alcohol per 100 mL of blood, plus 2.5 ng or more of THC per 1 mL of blood.
What happens if a police officer suspects impaired driving?
If a policer officer suspects cannabis impairment while someone is operating a motor vehicle (or if they suspect someone of being impaired while operating a motor vehicle within the preceding three hours), they can demand oral fluid samples (saliva) tested roadside with Approved Drug Screening Equipment (ADSE), which screens for THC.
Even if the fluid sample comes back negative, officers can still demand that you perform a Standardized Field Sobriety Test (SFST) — for example, an eye examination, standing on one leg and/or a walk-and-turn test. Refusing these tests can result in criminal charges that carry the same (or greater) penalties as driving while impaired.
If a driver fails roadside tests and is arrested, officers can then demand a blood sample (taken by a trained medical technician) and/or a 12-step Drug Recognition Expert Evaluation (DRE).
What if cannabis is in the car?
Every province and territory has its own laws for vehicle transport of cannabis. In Ontario, the law states that cannabis in the car must be:
- inside original packaging and unopened, or
- packaged and firmly sealed, or not otherwise readily accessible to the driver or passengers
Failure to keep cannabis contained and stored safely could result in charges.
When is it safe to drive after consuming cannabis?
There is no way to know exactly when it’s safe to drive after consuming cannabis. Unlike alcohol, there’s no scientific evidence to suggest a cannabis consumption limit safe for driving or a how long a driver should wait to drive, and the method of consumption adds even more uncertainty.
Some experts conclude that inhalation can impair your driving skills for six to eight hours, while ingesting cannabis can impair you for up to 12. It’s important to remember that everyone metabolizes cannabinoids differently, and even if a person feels sober, some effects of cannabis, such as drowsiness, can last 24 hours.
Tips for staying safe
To stay safe and within the limits of law, always err on the side of caution and have a plan to get home safely. You can:
- stay overnight
- call for a taxi or rideshare
- use public transit
- call a close friend or family member
- arrange for a designated driver
Knowing — and adhering to — the laws of your province or territory can help you stay safe after consuming cannabis.
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