Proper drug-driving test needed now, says B.C. researcher

B.C. experts are renewing calls for a systematic approach to drug-impaired driving after two U.S. studies suggested marijuana legalization has led to an increase in motor vehicle fatalities.

In Washington, marijuana-impaired driver fatalities rose from eight per cent in 2013 to 17 per cent in 2014. In Colorado, the number rose from three per cent in 2005 to 12 per cent in 2014.

In an editorial in the B.C. Medical Journal, Dr. Chris Rumball said the studies show a need for "a scientifically sound and fair approach toward drug-impaired driving."

Tim Stockwell, director for the Centre for Addictions Research of B.C. at the University of Victoria, agreed.

"There's no doubt that cannabis impairs one's ability to drive," he said. "We need rigorous testing and we need a very good system put in place ... and we need to move very quickly."

There is little deterrence when only a handful are convicted under the current system, he said, and people know they can get away with it.

"It's urgent with legalization impending that something is done with it."

While he commended the U.S. studies for putting the spotlight on drug-impaired driving, he cautioned the research deserves more scrutiny and follow-up research.

"It's something that's got to be looked at really closely," he said. "For example, [cannabis] can be detected for quite a long time after the incident itself ... so it's unclear when you detect cannabis in the system whether it was responsible for the death."

Different from alcohol-impaired driving

Follow-up research, Stockwell suggested, could help us better understand how marijuana impairs driving and what the limit should be.

"There's some tests to suggest people under the influence of cannabis drive more slowly and are more risk averse ... it depends very much on the dose," he explained.

Research could also help develop a better test to measure marijuana impairment.

"You'd need to have a mobile testing unit for maximum benefit ... to make rapid, quick tests and confirmation at the roadside," he said.

The federal government is expected to introduce legislation legalizing marijuana in the spring of 2017.

With files from The Early Edition

To hear the interview, click on the link labelled Does marijuana use cause an increase in motor vehicle accidents?