Webinar Series

Marijuana Use Among Drivers in Canada

July 22, 2020   |   Categories: Webinar Series

Presenter

Dr. Heather Woods-Fry is a research scientist with the Traffic Injury Research Foundation (TIRF), a charitable, independent road safety research institute. TIRF is a world leader in research, safety programs, and policy development.  Heather conducts research in various areas of road safety, such as drug-impaired driving, driver training and education, automated vehicles, older driver safety, and cyclist safety. She is fluent in both English and French, and has liaised with both national and international stakeholders. Some of her projects include the development of a web-based educational tool on drug-impaired driving, the realization of the Graduated Driver Licensing (GDL) Framework Safety Center to help states strengthen young driver safety strategies, and the evaluation of BikeMaps.org, a mobile app using crowd sourcing for citizen mapping of bicycle crashes, near misses, and hazards. She has authored several peer-reviewed academic articles and co-authored reports and on a variety of road safety topics. Before working at TIRF, Heather completed her graduate degree in the area of behavioural psychology, with a focus on driver safety. Her work included a three-phase driving simulator research program that was part of a part of a
nationwide longitudinal study on older driver assessment.

Title of Abstract

Marijuana Use Among Drivers in Canada

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.