The legalization of recreation cannabis in Canada in 2018 led to new laws and penalties around driving under the influence of cannabis (and other drugs), new screening and testing measures to detect impaired drivers and new education and awareness efforts to emphasize the risks and consequences of driving high. Here, MADD Canada answers some of the key questions we have been receiving about cannabis legalization and driving under the influence of cannabis.

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What is Cannabis?

Cannabis is a drug used for recreational and medical purposes. It is derived from the cannabis sativa plant, which contains chemical substances known as cannabinoids. Cannabinoids affect cell receptors in the brain and body, and how those cells behave and communicate with each other.

The most well-known cannabinoid is THC, or tetrahydrocannabinol. This is the component responsible for the high or intoxicating effect of cannabis. THC comes in varying strengths or potency, and that can directly impact the effects of the chemical. The potency of THC has increased over the years.

Another well-known cannabinoid is CBD or cannabidiol. This substance does not cause a high or intoxicating impact, and is often used for therapeutic purposes. There is some evidence that CBD may block or lower some of the effects of THC on the mind.

Cannabis comes in various forms and can be consumed in different manners. Not all forms of cannabis will be immediately available for legal sale under the Cannabis Act. For more information, please see:

What are the effects of cannabis?

THC (tetrahydrocannabinol), the main active ingredient in cannabis, impacts specific targets in the body, known as cannabinoid receptors. Cannabinoid receptors are found in most tissues and organs in the body, but are most numerous in the brain and nervous system. Cannabinoid receptors are involved in the regulation of many bodily functions, including: brain and nervous system activity; heart rate and blood pressure; digestion; inflammation; immune system activity; perception of pain; reproduction; wake/sleep cycle; regulation of stress; and emotional state.

The short-term effects of cannabis can include:

  • euphoria, feeling high;
  • relaxation; and
  • heightened sensory experiences (sight, taste, smell, sound).

While cannabis has the effect of making one feel relaxed and happy, the brain may also experience negative or unpleasant effects, including confusion, sleepiness and/or impaired ability to remember, concentrate or react quickly. It may also cause anxiety or panic.

Cannabis can have short and long-term effects on the mind and body. For more information, please see:

Does cannabis affect driving ability?

Many drugs impair one’s ability to drive. Depending on the drug type, it can reduce alertness, alter depth perception, impair concentration and attention span, slow reaction time, and affect motor skills and visual function. Many people think driving under the influence of cannabis is risk-free, and that drivers on cannabis are more cautious and driver slower. But studies show that cannabis can have a negative impact on driving, including reduced concentration and attention span, slower reaction time, and an altered perception of time and distance. Driving studies (simulated and on-road) showed drivers had increased variability in lane position, following distance and speed following cannabis use. Cannabis also affected driver ability to react to unexpected events, such as a pedestrian darting out onto the roadway.
(Source: Clearing the Smoke on Cannabis Cannabis Use and Driving – An Update. Canadian Centre on Substance Use and Addiction. Douglas J. Beirness, Ph.D., Senior Research Associate, CCSA, Amy J. Porath, Ph.D., Director, Research and Policy, CCSA.)

Mixing cannabis with alcohol greatly increases the negative impact on driving skills. A recent study comparing British Columbia roadside survey results with post-mortem data on fatally-injured drivers reported that cannabis use alone increased the risk of a fatal crash fivefold and that cannabis use, when combined with alcohol, increased the risk fortyfold.
(Source:A comparison of drug use by fatally-injured drivers and drivers at risk. D. Beirness & E Beasley & P. Boase. Canadian Centre on Substance Use and Addiction, and Transport Canada. Proceedings of the 20th International Conference on Alcohol, Drugs and Traffic Safety, 2013,)

For more information:

How risky is driving after cannabis use?

Estimates vary on the relative risk of crash associated with cannabis use. While there needs to be additional research in this area, studies and surveys over the past several years do indicate an increased risk of crash following cannabis use.

Studies estimating the number of crash deaths attributable to cannabis are concerning.

Rates of driving after cannabis use and related crash deaths and injuries may have increased in the last several years, as a result of rising usage rates of medical and recreational cannabis. The experience in Colorado and Washington, following the legalization of cannabis, also suggest an increased crash risk.

  • The percentage of cannabis-positive drivers in fatal crashes in Colorado, which had been decreasing, increased following legalization, and that increase was higher than in those states which had not legalized cannabis. (Source: S. Salomonsen-Sautel et al., “Trends in fatal motor vehicle crashes before and after marijuana commercialization in Colorado” (2014) 140 Drug and Alcohol Dependence 137, at 140. The authors also reported that there were no significant changes in the percentage of alcohol-impaired drivers in fatal crashes in either Colorado or the Non-Medical Marijuana States.)
  • A Washington State study showed the percentage THC-positive drivers in fatal crashes approximately doubled in the year after recreational cannabis use was legalized. (Source: B. Tefft, L. Arnold & J. Grabowski, “Prevalence of Marijuana Involvement in Fatal Crashes: Washington”, 2010-2014 (Washington, DC: AAA Foundation for Traffic Safety, 2016), at 1.)

Researchers note, and MADD Canada recognizes, that the simple presence of cannabis does not mean a driver is impaired. However, roadside surveys often find levels of cannabis high enough to impact driving ability. A 2010 British Columbia roadside screening study, for example, reported the majority of cannabis-positive drivers found had THC levels over 40ng/ml. The authors noted that the readings point to cannabis use just prior to or while driving, and they concluded that the vast majority of cannabis-positive drivers had THC levels that impaired their ability to drive safely. (Source: D. Beirness & E. Beasley, Alcohol and Drug Use Among Drivers: British Columbia Roadside Survey 2010 (Ottawa: Canadian Centre on Substance Abuse, 2011), at 12 and 13

The Canadian Centre on Substance Use and Addiction estimates the annual cost related to cannabis-involved collisions in Canada to be $658 million.

How common is cannabis use among drivers?

MADD Canada’s statistical research has shown a growing incidence of driving after drug use. The number of fatalities involving drugs alone is double those involving alcohol alone. Cannabis, the most commonly-found drug, is present in almost half of the drug-positive fatal crashes.

In 2014, road crashes claimed an estimated 2,297 lives. Based on testing of fatally-injured drivers, MADD Canada estimates 1,273 (55.4%) of these deaths resulted from crashes in which an individual was positive for alcohol and/or drugs:

  • 299 deaths, or 13%, occurred in crashes involving individuals who were positive for alcohol alone.
  • 618 deaths, or 26.9%, occurred in crashes involving individuals who were positive for drugs alone.
  • 356 deaths, or 15.5%, occurred in crashes involving individuals who were positive for both alcohol and drugs.

It must be emphasized that the figures document the presence of alcohol and/or drugs and not whether the individual was legally impaired. While research indicates that most of the alcohol-positive individuals were likely impaired or very impaired, there is no comparable information on the drug-positive drivers. However, it should be noted that the drug tests are designed to detect the recent use of psychoactive drugs that adversely affect driving skills, rather than metabolites that merely indicate use of the drug sometime in the past.

The prevalence of drug use among drivers is also reflected in recent studies and surveys.

  • A Statistics Canada report indicated that, In 2019, 13.2% of cannabis users with a valid driver’s license reported driving within two hours of using cannabis. The percentage of Canadians aged 15 years or older who were passengers in vehicles operated by drivers who had consumed cannabis within the previous two hours was 4.2%.  
  • A roadside survey conducted by Manitoba Public Insurance found that 10% of drivers tested positive for some form of drug (more than half of those tested positive for cannabis). Alcohol, by comparison, was found in 2.4% of drivers.
  • A study of young people in British Columbia found that more than three-quarters of frequent users reported having been in a car or other vehicle when the driver (including themselves) had been using marijuana or other drugs.

What are the signs of cannabis impairment?

Cannabis intoxication may have both physical and behavioural signs.

Physical signs:

  • eyes are red, watery or glassy;
  • smell;
  • dry mouth or shallow breathing; or
  • rapid heart rate.

Behaviour signs of cannabis intoxication:

  • delayed reaction time;
  • paranoia;
  • unfocused stares;
  • poor coordination; or
  • impaired judgement.

A person under the influence of cannabis may have both physical and behavioural signs of intoxication.

How long should you wait to drive after cannabis use?

It is hard to say exactly how long someone should wait after cannabis use before they drive. Everyone is different and the rate of dissipation can be affected by many things, such as how much was consumed and the potency of the cannabis.

Experts suggest waiting a minimum of four to six hours after cannabis use before driving. But that is the minimum, and everyone needs to understand there are a number of situations and scenarios that would require a longer wait time. New users, for example – people who aren’t used to consuming cannabis should wait longer. Users who have consumed a lot should wait longer. And certainly anyone who has combined cannabis with other drugs and/or alcohol should wait longer. We can’t emphasize enough that there are many factors involved. If you don’t feel right – if you don’t feel sober – don’t drive.

The safest option is to separate cannabis use from driving entirely. MADD Canada’s recommendation is the same as it is with alcohol – if you know you’re going to be consuming, don’t drive. Plan ahead for a sober ride home – take an Uber, a cab, a designated driver or public transportation. Driving impaired – whether it’s by cannabis, alcohol, or other drugs – is just not worth the risk.

What are the new laws and penalties for driving under the influence of drugs?

Bill C-46, passed in June 2018, established new federal laws and penalties around driving under the influence of cannabis and other drugs. Three new offences have been created in the Criminal Code of Canada:

  • Driving with 2 nanograms (ng) but less than 5 ng of THC per millilitre (ml) of blood.
  • Driving with 5 ng or more of THC per ml of blood.
  • Driving with a combination of 50 milligrams (mg) of alcohol (or more) plus 2.5 ng or more of THC per 1 ml of blood.

Along with THC, these offences apply for any detectable levels of other impairing drugs, including cocaine, methamphetamine, LSD, ketamine and others.

Federal Penalties for Drug-Impaired Driving

Penalties for drug impaired Source: Impaired Driving Laws (Department of Justice, Government of Canada)

Provincial/Territorial Drugged Driving Laws

Provinces and territories have constitutional authority over highways and the licencing of drivers within their jurisdiction, giving them the ability to enact additional laws and sanctions to complement the federal impaired driving laws. Most jurisdictions, for example, have administrative licence suspension for drivers with blood alcohol concentrations (BACs) between .05% and .08%, and zero alcohol requirements for young drivers until age 21 or 22. In preparation for the legalization of cannabis, most provinces and territories updated their impaired driving laws and penalties to include specific measures to address drug-impaired driving, including zero drug requirements for young drivers and commercial drivers, roadside licence suspensions for failure of a drug screening test, and mandatory education programing for offenders convicted of drug-related impaired driving offences. Provinces and territories also establish their own rules and regulations with respect to how and where cannabis is sold, legal age of purchase, purchase limits, if and where it can be publicly consumed, etc. Please check your provincial or territorial government web site for details on the new drug-impaired driving laws and various cannabis in your jurisdiction.

How do police test for cannabis use in drivers?

If police have reasonable suspicion that a driver has drugs in his or her body, the police can demand the driver complete a standardized field sobriety test (SFST) or provide an oral fluid sample (oral fluid testing devices are newly authorized for use by police as part of the Bill C-46 legislation). If the driver fails the administered test, the police can then demand a drug recognition evaluation (DRE) by specially trained officer or demand a blood sample for testing. As with testing for alcohol impairment, the first screening test is done at roadside (SFST or oral fluid screening tests) is not evidentiary and cannot be used as grounds to lay a charge or used as evidence in a criminal trial. Failure of the initial test gives police the grounds to demand a second, more sophisticated test. Failure of the secondary testing process provides grounds to lay a Criminal Code impaired driving charge.


Can I fail the test hours or days after consuming?

I have heard that traces of cannabis can stay in your system for a long time, even after the impairing effects are gone. Does that mean I could fail the test hours or days after consuming?

It is true that traces of cannabis can stay in one’s system for quite some time after consumption. While a background haze of THC may persist after use, the roadside oral fluid screening devices are set to a 25 nanograms threshold, which is significantly higher than the legal driving limits. In order to fail the roadside oral screening test, a driver must have above 25 nanograms per millilitre of THC in his or her oral fluid. Readings at this level are indicative of very recent use or a high level of impairment. Setting the screening devices to fail at 25 nanograms or higher reduces the risk of false positives, helping ensure that only those drivers who have recently used or are grossly impaired fail the test. The oral fluid test is only a screening test and cannot be used as evidence in a criminal trial; rather, those drivers that fail an oral fluid test will then be required to do a second evidentiary test, which can be used as evidence. It should also be noted that police will need reasonable suspicion that a driver has drugs in his or her body to demand a driver take the roadside oral fluid screening test in the first place. This remains a concern for medical cannabis users, whose trace cannabis levels will be higher than the recreational user. MADD Canada’s recommendation, as it is for users of other prescription drugs which may impact driving ability, is to always consult with the prescribing doctor and follow their advice on if and when it is safe to drive after taking the drug.

Snapshot of Canadian Cannabis Use and Driving after Cannabis Use

Statistics Canada’s report What Has Changed Since Cannabis Was Legalized provides a look at the rate of cannabis use among Canadians, as well as the rates of driving after cannabis use and riding with a driver who has recently used cannabis.

  • By 2019, more than 5.1 million Canadians (16.8% of Canadians aged 15 years or older) reported using cannabis in the three months before the survey.   
  • In 2019, 13.2% of cannabis users with a valid driver’s license reported driving within two hours of using cannabis. (That is unchanged since pre-legalization). Males were more likely to driver after cannabis use than females (15.6% compared to 9.4%). 
  • Between 2018 and 2019, the percentage of Canadians aged 15 years or older who were passengers in vehicles operated by drivers who had consumed cannabis within the previous two hours dropped to 4.2% from 5.3%. (However, these reductions were limited to three provinces – Newfoundland and Labrador, Alberta and Ontario.) 
  • Riding with drivers who had recently consumed cannabis was more common among 18- to 24-year-olds than it was for both younger and older Canadians. 

People were more likely to ride with someone who had used cannabis recently if they themselves were cannabis users. In 2019, 20.1% of users reported having been a passenger compared with 1.4% of non-cannabis users.

What is MADD Canada doing to educate Canadians about the risks of driving high?

Even with new laws around drug-impaired driving in place, there is a great deal of work still to be done. Public health and research groups are examining various questions related to cannabis use and cannabis-impaired driving, including a comprehensive study on the impact of cannabis on driving related skills by the Centre for Addiction and Mental Health. Community and road safety organizations are initiating campaigns and programs to educate the public about safe cannabis consumption and the risks of driving under the influence of cannabis. MADD Canada is proud to be doing our part to meet the challenge. From information in our school programs to new television, radio and online public service announcements, to web content and videos – we are informing and educating the public about the new laws, about the known impact of cannabis on driving, and about the importance of never driving impaired. We are working with provinces and territories to highlight and recommend the most effective legislation and policies to reduce drug-impaired driving, as well as the best practices in responsible cannabis retail sales to minimize public safety risks, including impaired driving. We are also proud to partner with sponsors to conduct broad public awareness campaigns to engage and educate Canadians about safe recreational cannabis use and the prevention of drug-impaired driving. Here is a look at some of our recent activities and partnerships.

  • Don’t Drive High Campaign from Tweed, Uber and MADD Canada emphasizes responsible cannabis use and alternate transportation options for those who have consumed cannabis. The campaign includes a creative list of 101 things that people can do instead of driving high and 40,000 $5 Uber vouchers to be given out to members of the public.
  • An array of television and radio public service announcements about the risks and consequences of driving under the influence of cannabis, alcohol or other drugs.
  • MADD Canada’s School Assembly Program and SmartWheels programs bring education on alcohol, drugs and driving to elementary, middle and high school students. We have also partnered with SpringBoard to deliver the Weed Out The Risk program to high school students.
  • Don’t Drive High Campaign – A education and awareness campaign with Public Safety Canada.
  • Partnering with Lift & Co. to provide comprehensive information and resources to its training program for retail cannabis sales staff.

Does MADD Canada accept funding from cannabis producers or retailers?

MADD Canada has sponsorship arrangements with Canopy Growth and Lift & Co. Such partnerships help us address the vital need to educate Canadians about the effects of cannabis on driving and the risks of driving while under the influence of cannabis. Working with our partners, we are able to significantly enhance these education and awareness efforts, and the number of people reached. The ultimate result will be a reduction in the number of Canadians who drive high. Such types of partnership are similar to the sponsorship relationships MADD Canada has had with various provincial liquor control boards, which a mandate for social responsibility campaigns. The key criteria for such relationships is always a focus on and commitment to social responsibility principles and outcomes.


What is CannSell?

CannSell is the approved certification training program for legally authorized cannabis retailers in Ontario. All employees of cannabis retail stores, store managers, and cannabis retail licence holders must complete the CannSell certification.

Developed by Lift & Co, in partnership with MADD Canada, CannSell educates cannabis retail staff on the responsible sale of cannabis, as well as their legal and regulatory obligations. The training will also provide basic knowledge about cannabis to ensure those who are selling it understand the various forms, effects and the potential risks and harms of cannabis use, including impaired driving.

For more information on the CannSell training program or to sign up to take the course, please visit, email Lift & Co at or call 1-800-681-1593.

Versions of the retail training certification program have also been delivered to retail sales staff of the Nova Scotia Liquor Corporation, Prince Edward Island Cannabis Management Corporation and numerous private retailers across the country.