The majority of Canadians will agree that the legalization of marijuana will seriously impact safety on our roadways. Studies have shown that between 2000 and 2010, 16.6% of fatally injured drivers tested positive for cannabis use.

A recent poll conducted by CAA found that two-thirds of Canadians are concerned that driving will become more dangerous following legalization. This same survey revealed that over a quarter of those surveyed felt they “drive okay or even better when impaired” by marijuana.

Legislation is now in place to establish the legal limit for THC (the active ingredient in marijuana that creates the “high”) in the blood. This is similar to the limits set for alcohol use (i.e. 0.08 percent blood alcohol concentration level). However, unlike alcohol, which effects physical co-ordination at relatively low levels, marijuana affects the way a person thinks and how a driver may react to an unexpected occurrence while driving.

If a motor vehicle accident occurs while one is operating a vehicle while impaired by cannabis, this may result in both negligence in a civil action and a criminal offence.


Alberta’s alcohol and drug-impaired driving offences and penalties were recently updated to coincide with the new federal drug laws, which came into effect on June 21, 2018.

If you are found driving over the criminal limits for blood-drug concentration levels, you are considered impaired. Police can lay a summary conviction charge against a person driving with between two and five nanograms of THC per millilitre of blood (subject to a maximum fine of $1,000). Charges may be laid either as a summary or indictable offence for those who have more than five nanograms of THC per millilitre of blood, which may lead to increased fines and jail time as penalties.

In addition to these charges and penalties imposed by the court, drivers in Alberta who are believed to be criminally impaired, who fail or refuse to provide a fluid sample, or are found to be over the legal limits for alcohol, cannabis, or a combination of drugs and alcohol, will be subject to the following sanctions:

  • Immediate 90-day licence suspension.
  • Immediate 3-day vehicle seizure (or 7-day seizure for a second and subsequent occurrence).
  • Mandatory remedial education.
  • One-year participation in a provincial ignition interlock program.

Drivers under the Graduated Driver Licensing (“GDL”) program are subject to a zero tolerance policy. If any amount of cannabis or illegal drugs are found in their blood, the driver will be subject to the same provincial sanctions that apply to alcohol, including:

  • Immediate 30-day licence suspension.
  • Immediate 7-day vehicle seizure.
  • Must remain in GDL program for two years and have no suspensions in the last year to graduate from the program.


Marijuana impairment can change driver behaviour. However, the amount of the drug that is needed to cause impaired driving and the extent to which it increases the risk of an accident is unknown. Each individual is affected by cannabis differently. Impairment can depend upon the method of consumption (smoked, inhaled, ingested), the quantity of cannabis consumed, and the variety of cannabis and its THC levels. There is no conclusive level of THC that is “safe” for everyone.

Cannabis has been found to impact a driver’s ability to safely operate a vehicle. Deficits such as reaction time, visual function, concentration, short-term memory, and divided attention have all been found in those impaired by marijuana. A driver’s ability to monitor and respond to more than one source of information at a time and respond to unexpected events, also known as divided attention tasks, has been found to be impaired by the use of cannabis.

A study completed at McGill University was looking at the impact of marijuana on the driving ability of 18 to 24-year-old occasional cannabis users in Canada. Researchers tested the performance of the participants in intervals up to five hours after consuming cannabis. They also tested drivers without cannabis as a baseline.

The research found that cannabis did not have any effect on simple driving tasks, such as braking, steering, or lane-keeping. However, significant impairments were found for complex driving tasks, such as merging, turning, or spotting a pedestrian on a roadway.


Two studies conducted by the Insurance Institute for Highway Safety and the Highway Loss Data Institute released last week in the U.S. found an increase in the number of car accidents in states that have legalized the recreational use of marijuana.

The first study found that car accidents in Washington, Oregon, and Colorado have increased up to 6% in comparison to their neighbouring states that have not legalized marijuana.

The second study found that there was a 5.2% increase in car accidents in states that have legalized marijuana use when looking at the number of police-reported traffic accidents prior to and following the legalization of marijuana for recreational purposes.


The best approach to avoid impaired driving is to plan ahead. There is no reason to drive while impaired or for being a passenger in a car with an impaired driver.

If you are planning on participating in the use of recreational marijuana, be sure to consider the following options:

  • As a parent make sure your child understands the dangers of driving under the influence and make sure he/she has money to take a taxi home.
  • Make sure you have a designated driver.
  • Call a friend or loved one to pick you up.
  • Take public transit.
  • Call a cab or a ridesharing service.
  • Stay overnight.

If you or a loved one have been injured in a motor vehicle accident that was caused by an impaired driver, you may be entitled to compensation for the damages you have suffered. Please contact the experienced lawyers at Cuming & Gillespie LLP either online or by calling 403-571-0555 for a free consultation.