Cannabis Legalization Part 2: Driving Impaired
October 22, 2018 By: Ludmilla Jarda and Paul Taylor-Sussex Read Time: 3 minutes
Print

Marijuana use was legalized in Canada last week, and while this has been over a year in the making, the many issues raised by the new law continue to be debated and discussed.

Where will I be able to purchase pot? Can I grow my own marijuana plants? Will I be able to smoke at work?

Driving high

One important aspect is how the legalization of marijuana will affect drivers.

As our previous post on this topic highlighted, research on drug-impaired driving conducted by Public Service Canada in 2017 found that 28% of marijuana users surveyed had operated a vehicle while under the influence of cannabis.

This post will look at the state of the law as it relates to drug impairment and driving, and what the repercussions are for being caught driving under the influence.

Is it safe to smoke pot and drive?

Much like alcohol, marijuana consumption impairs your ability to drive safely. So: no, it is not safe to smoke pot and drive.

Studies have shown that marijuana affects spatial perception and reaction times, thereby increasing the chance of getting into a collision, potentially harming yourself or others.

While people who consume marijuana may believe they can still drive safely, the reality is that if you under the influence of pot, then you are impaired and should not be driving.

Is it against the law to drive under the influence of marijuana?

The federal Criminal Code states that it is an offence to drive a car “while the person’s ability to operate the vehicle … is impaired by alcohol or a drug”. This obviously includes being impaired by marijuana use. The provinces are responsible for the enforcement of this law, as well as the prosecution and application of penalties. In Ontario, the Highway Traffic Act outlines the penalties for impaired driving.

Consequences for impaired driving can be severe, particularly for repeat offenders or if someone is injured. Fines begin at $250, and include jail time and driving prohibitions for more serious offences.

See more on Ontario’s Ministry of Transportation website here.

How is marijuana impairment tested?

While alcohol impairment is usually picked up via a roadside breathalyser, there is no such test for marijuana.

Canadian police officers rely on drug recognition experts (DREs) to determine impairment. The DREs conduct a sobriety evaluation similar to that used to observe alcohol impairment. As well as the sobriety test, clinical indicators are also taken, such as blood pressure and pupil size. Refusal to participate may result in criminal charges. However, as a recent CBC investigation discovered, the tests used by DREs are not definitive, and can be subjective.

Bill C-46 was passed at the same time as the Cannabis Act, and it aims to give police more power to detect and charge impaired drivers. This controversial bill allows police to test a driver for the presence of alcohol or drugs in their system (via a blood test) if they have “reasonable grounds” to believe the driver is under the influence. Concerns are that the tests may be invasive, open to abuse, and potentially could infringe constitutional rights (such as the right to retain legal counsel).

There is also concern about using levels of THC as a measure of impairment. The issue is that THC (the chemical in marijuana responsible for the “high”) is metabolized at different rates in different people. That is, some individuals may have traces of THC in their system, but will not actually be impaired. So it is not possible to determine impairment simply by testing for THC.

Can passengers in a car smoke pot?

Ontario’s Cannabis Act strictly confines marijuana use to private residences.

The Act states explicitly that “No person shall consume cannabis in … a vehicle”, which would therefore include the driver and all passengers.

Tips for drivers and passengers

Given the risks involved, you should never get in a car operated by a driver that you know has consumed marijuana, even if they do not appear to be impaired.

Where possible, you should try to plan ahead and arrange alternative transportation.


As a potential driver, it goes without saying that if you have consumed marijuana, you are not the best person to ascertain if you are impaired or not. When in doubt, don’t get behind the wheel.

Stay tuned for our next blog post on marijuana and driving, which will look at property damage claims.

For more information about marijuana and driving, contact our Personal Injury group.

This content is not intended to provide legal advice or opinion as neither can be given without reference to specific events and situations. © 2018 Nelligan O’Brien Payne LLP.