The effects of psychodynamic drugs such as cannabis, amphetamine, cocaine, and anti-depressants on driving vary by drug. They generally result in slower reaction time, failure to identify danger, poor decision-making, and falling asleep at the wheel. (For more information see: https://druggeddriving.tirf.ca/module/the-effects-of-drugs-on-driving/#tabid/1
Data from the National Collision Database (NCDB) indicate that in 2020, 3.5% of all fatal collisions in Canada involved a driver being impaired or under the influence of drugs which was similar to the percentage in 2017. Coroner data from National Fatality Database maintained by the Traffic Injury Research Foundation indicate that the 55% of fatally injured Canadian drivers tested positive for drugs in 2020 compared to 44% in 2017 an increase of 25%. The presence of cannabis increased from 22% in 2017 to 30% in 2020, an increase of 36%. The distribution by other drug classes in 2020 was as follows;
- 36% for CNS depressants;
- 36% for CNS stimulants;
- 19% for narcotic analgesics.
Night-time roadside surveys in five jurisdictions in 2017 and 2018 (British Columbia, Manitoba, Ontario, Yukon, and Northwest Territories) determined that 10.2% tested positive for the presence of at least one potentially impairing substance other than alcohol. The drivers who tested positive for cannabis represented 75% of drivers who had drugs present. In a 2012 British Columbia (BC) night-time survey, 7.4 % of drivers tested positive for one or more drugs, and of these, 44% had been using cannabis. In a 2018 BC survey, 8.5% of drivers tested positive for one or more drugs an increase of 15% compared to 2012.  Of the drivers who tested positive for drugs, 71% had cannabis present. In an Ontario roadside survey, drugs were detected in 10.2% of drivers in 2014 . This climbed to 14.2% in 2017, an increase of 39%. In 2014, 7.0% of drivers tested positive for cannabis which climbed to 10.6% in 2017 an increase of 51 percent.
A survey by the Traffic Injury Research Foundation in 2020 found that 22% of drivers admitted to driving within two hours after consuming cannabis during the last 12 months, more than double the percentage observed in 2017 (14%). 
Changes to the Criminal Code of Canada in 2018 added several new offences regarding driving and cannabis use:
- driving with Tetrahydrocannabinol (THC) levels over 2 nanograms per 100 ml of blood will result in a charge which on conviction will result in a fine of $1,000,
- driving with THC at a level over 5 nanograms per 100 ml of blood will result in an impaired driving charge,
- driving with a level over 2.5 nanograms per 100 ml of blood of THC and 50 mg per 100 ml of blood or more of alcohol will result in an impaired driving charge.
On conviction, the latter two offences are subject to the same penalties as alcohol impaired driving (i.e., fines, licence suspensions, jail).
Further information about cannabis impaired driving laws can be found at:
Police are often on the lookout for both alcohol and drug impaired driving. The 2018 changes to the CCC now allow police officers to demand saliva samples from drivers at the roadside to test for the presence of psychodynamic drugs.
Public awareness programs have been conducted by various governmental and non-governmental agencies regarding the effects of drugs such as THC on driving and the consequences of being convicted of drug impaired driving.
Drug Impaired Driving FAQs:
- Transport Canada (2023) Canadian Motor Vehicle Traffic Collisions Statistics: 2021.
- Robertson, R. and Brown, S. 2023, Using Cannabis-Impaired Driving Research to Inform Policy, Webinar presented to CARSP).
- Beirness, D. J. (2020). A Compilation of Jurisdictional Roadside Surveys Conducted Prior to Cannabis Legalization. Report prepared for Canadian Council of Motor Transport Administrators.
- Beirness, D. J. and Beasley, E.E. (2019) Alcohol and Drug Use by Drivers in British Columbia: Findings from the 2018 Roadside Survey, Beirness Associates Inc.
- Beirness, D. J. (2018) Alcohol and Drug Use by Drivers in Ontario: Findings from the 2017 Roadside Survey, Beirness & Associates Inc.
- Woods-Fry, H. Robertson, R. D. & Vanlaar, W. G.M. (2020) Road Safety Monitor 2020: Trends in Marijuana Among Canadian Drivers. Traffic Injury Research Foundation, November 2020