Grant: Project Grant

Marijuana is the second most widely used recreational drug in the world after alcohol. It impairs the skills required for safe driving, and increases the risk of car crashes. The Canadian federal government will introduce laws to legalize marijuana in Apr 2017. It will then take approximately 18 months for the laws to be passed and put into force. Legalization of marijuana may result in more car crashes caused by drivers who are impaired by marijuana and this potential problem should be evaluated. Since 2011, the CIHR funded "Cannabis and Motor Vehicle Crashes" (CMVC) study has collected data on how often injured drivers in British Columbia test positive for marijuana, alcohol, and other drugs. This presents a unique opportunity. We propose to continue the same procedures as the CMVC study to investigate changes in the percentage of injured drivers who test positive for recent marijuana use following legalization of cannabis. Our aim is to inform policy targeting marijuana impaired driving. Our primary objective is to compare the percentage of injured drivers who test positive for marijuana after it is legalized versus before it was legalized. Our second objective is to get better estimates of how the risk of having a car crash varies with higher levels of THC (the active ingredient of marijuana). This information might help establish legal limits for driving after using marijuana.