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Cannabis-impaired driving: what you need to know

Most Quebec drivers have a good understanding of the rules around drinking and driving (i.e. zero tolerance for those under 21 and, for everyone else, a blood alcohol level not exceeding 0.08, or 80 milligrams of alcohol for every 100 millilitresof blood). But now that cannabis has been legal for several months, many people still have questions about driving under the influence of cannabis. For instance, many are wondering how long after using the drug they need to wait before they’re fit — and legally allowed — to take the wheel.

The team at Auto-Value has examined these matters in depth. Keep reading to get the facts about driving under the influence of cannabis.

What are the effects of cannabis consumption on driving?

Cannabis consumption affects your driving in a number of ways, including the following:

    •Slowing your reflexes and reaction time
    •Reducing your ability to concentrate
    •Impairing your motor co-ordination
    •Reducing your alertness

 If I’ve smoked cannabis, how long do I have to wait before driving?

According to a number of scientific studies, it’s “reasonable” to drive four to six hours after having smoked cannabis. But if the drug is ingested, the time frame is longer. However, no guidelines of this kind will be applicable to everyone, for there are a number of individual factors at play, including:

    •The gender, height and weight of the person
    •His or her level of tiredness
    •The concentration of THC in the cannabis
    •How often the person consumes the drug

What happens if I’m pulled over for driving under the influence of cannabis?

If you’re pulled over by a police officer and he or she suspects you’re under the influence of cannabis, you will have to submit to physical co-ordination tests or take a saliva test. If you don’t pass these tests, you’ll be driven to the police station, where more advanced tests will be done (for instance, blood or urine tests).

If these tests show that you had a quantity of the drug in your blood surpassing the legal threshold as determined by federal law (2 nanograms or more of THC per millilitre of blood), criminal charges can be filed against you.

Note: In Quebec, amendments to the Highway Safety Code comprising a “zero drug tolerance” policy were adopted in 2018. To learn more about this, visit

The dangers of cannabis-impaired drivingare clear and the strict new laws reflect this. If you’ve smoked or eaten cannabis, never get behind the wheel. If you need to get somewhere, call a taxi or use public transport. At Auto Value, we always encourage safe driving. And by keeping your vehicle in the best shape possible, we make you that much safer on the road. To make an appointment, contact one of our Certified Service Centres..

Service is the difference. We get it!

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