Marijuana Use Among Drivers in Canada
Author(s): Vanlaar, Robertson, Brown, Woods-Fry, Lyon
Slidedeck Presentation:
Slidedeck link
Abstract:
Background:
Public concern about drugged driving, particularly marijuana-impaired driving, is increasing. However, understanding of marijuana’s effects on driving behaviour is limited compared to what is known about alcohol. With the legalization of recreational marijuana in Canada in October 2018, continued monitoring of this issue is important to inform decision-making.
Aims:
To determine whether marijuana use among drivers in Canada is increasing and if certain subpopulations are more inclined to drive after using marijuana.
Methods:
TIRF’s online public opinion survey, the Road Safety Monitor (RSM), asks a random, representative sample of Canadian drivers about key road safety issues. It was used to measure attitudes, opinions and self-reported behaviours on 1) personal marijuana use, 2) driving after using marijuana, 3) perceptions of whether marijuana impairs driving as much as alcohol, and 4) levels of concern about marijuana-impaired driving. TIRF’s National Fatality Database, a unique source of data based upon both coroners/medical examiners data and police-reported collision data, was used to examine fatally injured drivers from 2000-2016 in terms of 1) trends in testing rates, 2) percentage of drivers testing positive, 3) positive tests based upon driver age, sex, vehicle type, and number of occupants, and 4) marijuana use combined with alcohol and other substances.
Results:
In 2019, 7% of respondents admitted to driving within two hours of using marijuana compared to 3.3% in 2018. There has been a significant increase since 2013, most notably since 2018. There were no significant changes in respondents’ opinions between 2016 and 2019 on whether marijuana was as impairing as alcohol. However, those who believed that marijuana does not impair one’s driving as much as alcohol increased significantly from 2018 to 2019 (10.3% to 15.7%). Since 2011, testing rates for marijuana use have improved as over 80% of fatally injured drivers have been tested compared to less than 50% between 2000 and 2010. The percentage of fatally injured drivers who tested positive for marijuana generally increased from 15.9% in 2000 to 23.3% in 2016. While 16-19 year old drivers were usually the most likely to test positive for marijuana, in some years, a comparable percentage of 20-34 year old drivers tested positive. Male drivers were twice as likely as female drivers to test positive for marijuana. Motorcyclists were more likely to test positive for marijuana than drivers of other vehicles. Of concern, among all fatally injured drivers testing positive for marijuana, 69% tested positive for at least one other impairing substance, mostly alcohol.
Discussion:
As self-reported marijuana use while driving continues to increase, it is expected that the number and percent of fatally injured drivers testing positive will also increase.
Conclusions:
A ‘one size fits all’ approach to reduce drug impaired driving among all age groups may not resonate equally throughout the driving population. There are merits to continuing to monitor public attitudes and behaviours on marijuana and driving in order to tailor safety messages. Similarly, it is important to track the prevalence of those testing positive for marijuana among all fatally injured drivers and within subpopulations.