Skip to content
Join our Newsletter

4/20 doubles risks of fatal road accidents: UBC study

Researchers use U.S. accident data to issue warning to legislators

As legislators draft Canada’s laws to legalize marijuana, a UBC researcher is encouraging them to pay special attention to the rules around consuming marijuana and driving.

Dr. John Staples, a clinical assistant professor of medicine and scientist at UBC’s Centre for Health Evaluation and Outcome Sciences, was lead researcher of a study that indicates drivers in the United States are more likely to be in a fatal traffic crash on 4/20.

“Assuming fewer than 10 per cent of Americans drive while high on April 20, our results suggest that drug use at 4/20 celebrations more than doubles the risk of a fatal crash,” said fellow researcher, University of Toronto professor Dr. Donald Redelmeier.

The study found that April 20 was associated with a 12 per cent increase in the risk of a fatal traffic crash. Among drivers younger than 21 years of age, the risk was 38 per cent higher than on control days. The overall increase amounted to 142 additional deaths over the 25-year study period.

Staples and Redelmeier examined 25 years of National Highway Traffic Safety Administration data on all fatal traffic crashes in the United States. They compared the number of drivers involved in fatal crashes after 4:20 p.m. on April 20 with the number of drivers involved in fatal crashes during the same time intervals on control days one week earlier and one week later.

The researchers didn’t know how many drivers drive while high. A 2011 study of U.S. College freshman found 44 per cent of U.S. college freshmen had driven after consuming marijuana.

Half of the cannabis users who responded to the 2017 Canadian Cannabis Survey thought that cannabis use did not affect their driving.

Staples and Redelmeier hope that authorities will respond to these results by encouraging safer 4/20 travel options, including public transit, rideshares, taxis and designated drivers. The investigators also note that cannabis retailers and 4/20 event organizers have an opportunity to serve their customers and save lives by warning users not to drive while high.

As Canada moves toward legalization, Staples says it’s also important to employ multiple strategies to reduce driving under the influence of drugs throughout the year.

“Driving is a potentially dangerous activity,” Staples said. “Improving road safety requires both policymakers and drivers to make smart decisions. If you’re going to get behind the wheel, buckle up, put the phone away, don’t speed, stay sober and don’t drive high.”