Cannabis prohibitionists often cite increased traffic accidents as one of many reasons not to legalize cannabis. Researchers investigated these claims and published the results in the journal Drug and Alcohol Dependence to get to the bottom of these claims. After analyzing Alberta and Ontario emergency department data from April 2015 to December 2019, researchers found no evidence of increased traffic danger post-legalization.

“Implementation of the Cannabis Act was not associated with evidence of significant post-legalization changes in traffic-injury [emergency department] visits in Ontario or Alberta among all drivers or youth drivers, in particular,” the study states.

In a press release, Russ Callaghan, the study’s lead author, said that his team’s results “show no evidence that legalization was associated with significant changes in emergency department traffic-injury presentations.” 

In 2019, experts tasked by the US House and Senate found inconclusive evidence around cannabis’s ability to impair driving. A study published by the Journal of the American Medical Association found that small doses of THC were associated with short-term impairment “similar to that seen in drivers with a 0.05%” blood alcohol concentration.

Callaghan admitted he was surprised by the results and said that he “predicted that legalization would increase cannabis use and cannabis-impaired driving in the population and that this pattern would lead to increases in traffic-injury presentations to emergency departments.”

Not entirely convinced by his own report, Callaghan referred to a separate impaired driving bill, saying, “It is possible that our results may be due to the deterrent effects of stricter federal legislation, such as Bill C-46, coming into force shortly after cannabis legalization.” 

The AAA Foundation for Traffic Safety recently raised concerns about the connection between marijuana use and serious traffic accidents. A 2020 report compared data about fatal accidents in Washington before and after recreational marijuana was legalized. Before the legalization of marijuana, about 8.8% of drivers involved in fatal traffic crashes tested positive for THC. During the 12-24 months after legalization, the percentage more than doubled, to 18%. By 2017, 21.7% of drivers involved in fatal accidents were THC-positive.

This data is far from definitive because testing positive for THC doesn’t correlate with being impaired by cannabis at the time of incident. While the intoxicating effects of cannabis typically wear off within a few hours, THC is detectable in the blood for much longer afterward (sometimes up to one or two months, depending on the person and their consumption habits).

While the various studies’ results are somewhat conflicting for different regions, one thing remains abundantly clear: driving under the influence is never okay. Whether it’s before or during, whether it’s rolling papers or water pipes, don’t smoke and drive! Enjoy cannabis responsibly. And on that note, check out this piece of ours talking about CBD and driving safety!