Drug Impaired Driving
The effects of psychodynamic drugs such as cannabis, amphetamine, cocaine, and anti-depressants on driving vary by type of drug. They generally result in slower reaction time, failure to identify danger, poor decision-making, and falling asleep at the wheel.
For more information about the effects of drugs on driving see: Drug-Impaired Driving: Effects of Drugs on Driving (TIRF)
Prevalence:
Data from the Transport Canada’s National Collision Database (NCDB) for 2023, indicates that according to investigating police officers, 22%of fatal collisions involved a driver who was impaired or under the influence of alcohol and/or drugs. In 2020, the percentage for fatalities was 20%. Canadian Motor Vehicle Traffic Collision Statistics: 2023
data from National Fatality Database maintained by the Traffic Injury Research Foundation indicate that 38% of fatally injured Canadian drivers tested positive for drugs in 2021 compared to 30% in 2016, an increase of 27%. The presence of cannabis increased from 22% in 2017 to 28% in 2021, an increase of 27%. Drug Use in Fatal Collisions 2000–2021 (TIRF)
Night-time roadside surveys in five jurisdictions in 2017 and 2018 (British Columbia, Manitoba, Ontario, Yukon, and Northwest Territories) determined that 10% of drivers 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. Compilation of Jurisdictional Roadside Surveys Before Cannabis Legalization (Sept 2019, CCMTA)
In a 2012 British Columbia (BC) night-time survey, 7 % of drivers tested positive for one or more drugs, and of these, 44% had been using cannabis. In a 2018 BC survey, 8% of drivers tested positive for one or more drugs, an increase of 14% compared to the 2012 survey. Of the drivers who tested positive for drugs, 71% had cannabis present. Roadside Survey Findings, 2018 (British Columbia)
In an Ontario roadside survey, drugs were detected in 10% of drivers in 2014. This climbed to 14% in a 2017 survey, an increase of 40%. In 2014, 7% of drivers tested positive for cannabis which climbed to 11% in 2017, an increase of 57 percent. Impaired Driving in Canada: 2024 Policy Brief (CCSA)
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, 57% more than the percentage observed in 2017 (14%). RSM 2019: Marijuana Use by Canadian Drivers
Detection of Cannabis Impaired Driving:
The police use the Standardized Field Sobriety Test (SFST) at the roadside to determine whether a driver is impaired by alcohol and other drugs such as cannabis. Beirness, et al. (2024) conducted a study for the Canadian Centre on Substance Use to explore various tests of impairment that could potentially be added to the Standardized Field Sobriety Test (SFST) to enhance its sensitivity to identify drivers whose abilities are adversely affected by cannabis.
Once prior to cannabis use and at four times during the 150 minutes after cannabis use, participants performed the three tests of the Standardized Field Sobriety Test (SFST) (i.e., Horizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand) as well as the Modified Romberg Balance and Finger to Nose tests.
Twenty minutes after vaping cannabis (mean THC concentration = 6.34 ng/mL), participants displayed performance deficits on a variety of tasks; 67% met the criterion for suspected impairment on the SFST. The addition of the Finger-to-Nose (FTN) test along with observations of head movements and jerks (HMJ) increased the percentage of participants who met the criterion for suspected impairment by 33% and improved the sensitivity of the test from 0.67 to 0.88.
The results of this study support supplementing the SFST with the Finger-to-Nose test and observations of HMJ to assist in the detection of drivers who are adversely affected by the use of cannabis.
Countermeasures:
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 100ml 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 on these charges, 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:
- Pot + Driving: FAQs (2018, Canadian Public Health Association)
- Cannabis-Impaired Driving Laws | CAA Canada
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.
For example: