The risk of a fatal accident among young drivers spikes by 38 per cent in the hours after 4/20 celebrations, according to new research from UBC and the University of Toronto.
The finding suggests that mass marijuana celebrations may not be entirely without consequences.
John Staples, a professor and researcher at UBC’s Centre for Health Evaluation and Outcome Sciences, said people aged 20 and younger had a much higher risk of a fatal crash on April 20, from 4:20 p.m. until midnight, compared to the same period one week before and one week after.
Governments contemplating policies to deter so-called drugged driving in the wake of cannabis legalization should pay special attention to young drivers, he said.
“It was a dramatic effect with that young group,” he said. “We know that younger drivers are more vulnerable, because they lack experience and possibly due to risk taking behaviour.”
B.C. is preparing new regulations in anticipation of the nationwide legalization of recreational cannabis planned for July 1 and at that time anyone over the age of 19 will be able to purchase and possess up to 30 grams of marijuana for recreational use.
Earlier this week, Solicitor General Mike Farnworth said the provincial government will impose a 90-day driving ban for drug-impaired drivers. He also promised increased training for police to recognize impairment and zero tolerance for cannabis for drivers in the graduated licensing program.
It is not clear how impairment will be defined and whether there is a reliable test for impairment due to cannabis intoxication.
“It’s before the Senate and it’s one of the areas I’ve said where we have real concern about the equipment, the test that’s being used and when it will be ready,” Farnworth told reporters.
Staples and UofT professor Donald Redelmeier examined 25 years of National Highway Traffic Safety Administration data on all fatal traffic crashes in the United States between 4:20 p.m. and 11:59 p.m. on April 20 and the same period a week after and before.
The analysis, published in the Journal of the American Medical Association, revealed a 12 per cent increase in fatal crashes across all age groups on April 20 after 4:20 p.m.
Recent 4/20 celebrations in major cities have attracted tens of thousands of revellers since becoming popular in 1991. The celebrations often feature synchronized mass consumption of cannabis at exactly 4:20 p.m.
Data that definitively link these fatal crashes to cannabis intoxication does not exist, because testing regimes vary dramatically between states.
“It’s a remarkable number and a pretty straightforward natural experiment,” said Staples. “The simplest explanation is that some drivers are impaired by cannabis and these drivers contribute to fatal crashes.”
A report on B.C.’s roadside survey results published in 2012 noted that 33 per cent of fatally injured drivers in Canada tested positive for psychoactive drugs.
The survey — which collected samples from drivers in five B.C. cities — found that 6.4 per cent of drivers tested positive for alcohol, while 10.1 per cent tested positive for other drugs.
The vast majority of the drug-positive tests indicated the driver had been using cannabis or cocaine, but not whether they were legally impaired.
It is not clear whether legalization will encourage more people to use cannabis or how and when people will consume the drug.
Under B.C.’s new rules, cannabis will be allowed anywhere people can legally smoke tobacco or use vaping products, though it will be illegal in vehicles and in places frequented by children, including beaches, parks and playgrounds.
“The most important work for researchers and the government to be doing right now is to determine what we can do make the roads as safe as possible,” said Staples.
With a file from Derrick Penner.