Research Papers

Estimating the harms and costs of cannabis-attributable collisions in the Canadian provinces

Version 1
Date added June 28, 2017
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Category 2017 CARSP XXVII Toronto
Tags Research and Evaluation, Session 6A
Author/Auteur Doug Beirness, Sameer Imtiaz
Stream/Volet Research and Evaluation

Slidedeck Presentation Only (no paper submitted)



In 2012, 10% of Canadians used cannabis and just under half of those who use cannabis were estimated to have driven under the influence of cannabis. Substantial evidence has accumulated to indicate that driving after cannabis use increases collision risk significantly. Little is known about the extent and costs associated with cannabis-related traffic collisions. This study quantifies the harms and costs of cannabis-related traffic collisions in the Canadian provinces. Province and age specific cannabis-attributable fractions (CAFs) were calculated for traffic collisions of varying severity. The CAFs were applied to traffic collision data in order to estimate the total number of persons involved in cannabis-attributable fatal, injury and property damage only collisions. Social cost values, based on willingness-to-pay and direct costs, were applied to estimate the costs associated with cannabis-related traffic collisions. The 95% confidence intervals were calculated using Monte Carlo methodology. Cannabis-attributable traffic collisions were estimated to have caused 75 deaths (95% CI: 0- 213), 4,407 injuries (95% CI: 20- 11,549) and 7,794 people (95% CI: 3,107- 13,086) were involved in property damage only collisions in Canada in 2012, totalling $1,094,972,062 (95% CI: 37,069,392- 2,934,108,175) with costs being highest among younger people ages 16 to 34 years old. Our results suggest that driving under the influence of cannabis (DUIC) has a substantial impact on collision rates and attendant costs in Canada. The greatest burden is on young and novice drivers under the age of 34; this means that these cost estimates are likely to be conservative since the cost values applied here do not account for the victims' age. The findings of this research suggest that it could be important to further explore DUIC among young drivers. The harm and cost of cannabis-related collisions is an important factor to consider as Canada looks to legalize and regulate the sale of cannabis. This analysis provides evidence to help inform Canadian policy to reduce the human and economic costs of drug-impaired driving.

Doug Beirness, Sameer Imtiaz