On October 17 2018, the recreational use of cannabis became legal in Canada. With that came new laws and penalties around driving under the influence of cannabis (and other drugs), new screening and testing measures to detect impaired drivers and new education and awareness efforts to emphasize the risks and consequences of driving high. Here, MADD Canada answers some of the key questions we have been receiving about cannabis legalization and driving under the influence of cannabis.
Many drugs impair one’s ability to drive. Depending on the drug type, it can reduce alertness, alter depth perception, impair concentration and attention span, slow reaction time, and affect motor skills and visual function. Many people think driving under the influence of cannabis is risk-free, and that drivers on cannabis are more cautious and driver slower. But studies show that cannabis can have a negative impact on driving, including reduced concentration and attention span, slower reaction time, and an altered perception of time and distance. Driving studies (simulated and on-road) showed drivers had increased variability in lane position, following distance and speed following cannabis use. Cannabis also affected driver ability to react to unexpected events, such as a pedestrian darting out onto the roadway.
(Source: Clearing the Smoke on Cannabis Cannabis Use and Driving – An Update. Canadian Centre on Substance Use and Addiction. Douglas J. Beirness, Ph.D., Senior Research Associate, CCSA, Amy J. Porath, Ph.D., Director, Research and Policy, CCSA.)
Mixing cannabis with alcohol greatly increases the negative impact on driving skills. A recent study comparing British Columbia roadside survey results with post-mortem data on fatally-injured drivers reported that cannabis use alone increased the risk of a fatal crash fivefold and that cannabis use, when combined with alcohol, increased the risk fortyfold.
(Source:A comparison of drug use by fatally-injured drivers and drivers at risk. D. Beirness & E Beasley & P. Boase. Canadian Centre on Substance Use and Addiction, and Transport Canada. Proceedings of the 20th International Conference on Alcohol, Drugs and Traffic Safety, 2013,)