Smoking pot within three hours of driving doubles your chance of a major crash, Canadian researchers have found.
Their study, published Thursday in the British Medical Journal, the first to tackle the link between crashes and cannabis use, examined data from more than 49,411 vehicular crash victims and excluded any incidents involving alcohol.
“The level of impairment might not be as severe as alcohol intoxication, but it’s there and it does require a public health response,” expert Wayne Hall told ABC Science.
The researchers said more information is needed to determine the level of tetrahydrocannabinol (THC)- the active compound in marijuana – that causes impairment in driving competence.
But there is a positive link between THC levels and crash risk, the data show.
Despite the clear danger of driving high, law enforcement agencies have very few tools to address the problem, the expert said, despite the fact that that marijuana is the second-most sited substance in motor vehicle incidents.
Although it is easy to measure blood alcohol levels using a breath test, it is much harder to determine concentrations of THC in the saliva and gauge driver impairment on the spot, Hall added.