How high is 'too high' for driving?: Research ongoing

As Saskatchewan ponders how to handle relaxed laws concerning marijuana and road safety, researchers in the field say a lot a of work needs to be done.

Premier Brad Wall said Wednesday that he asked ministers responsible for Justice, Corrections and Policing and officials from Saskatchewan Government Insurance (which oversees driver licensing) to examine how marijuana legalization will affect drivers and road safety.

A recent study on the topic was done at University of Iowa between 2012 and 2104.

Their trial included 19 occasional cannabis users and examined how they performed in a standardized driving simulator after using cannabis.

"We found a few different detrimental effects on driving performance," Andrew Spurgin, one of the researchers, said. "Some effects that we noted were that subjects seemed to weave more, in their lane."

Different behaviour compared to drinking and driving

Spurgin said the researchers also found a difference between weaving while under the influence of cannabis compared to alcohol.

"We didn't note that these participants were actually leaving their intended lane of travel more often," he said. "Which was a very interesting finding."

He said the cannabis users also drove slower, a finding which he said was not surprising. Spurgin noted that moving at a reduced speed may be hazardous, in certain situations.

The trial also tried to consider the degree to which the subject was impaired by cannabis. He said all the people in the trial had some previous, regular, experience with the drug.

While different doses were administered, Spurgin said relating behaviour between medium users and heavier users was difficult.

"That's the question we're all trying to answer," Spurgin said when asked how high is too high to drive. "This study was just the tip of the iceberg in terms of marijuana's effects on driving performance."

He said the whole topic was "surprisingly understudied" when it comes to impaired driving research.

"That has, largely, to do with the legal hoops that you have to jump through as a researcher to actually use cannabis," he said, noting the different laws in the U.S.

Spurgin said existing measurements for drinking and driving, using a blood-alcohol content reading, do not translate to cannabis.

"What we can't come up with, at the current time, with the information that we have, is the magic number, [for marijuana]" he said.

Testing is a challenge

Another challenge, he said, concerned how traces of the drug remain in the body even after its effects have subsided. He noted how the measurement of the drug, in the body, lacks standardization.

Spurgin said research is also looking into a portable tester that analyses a swab from the inside of the cheek.

"That has a lot of promise," he said, as the test could provide information on recent drug use. "But I don't think the technology is there yet."

Spurgin said the way the body metabolises cannabis adds to the testing challenge as it may not always reflect current information on drug use.

"So its really hard to get an accurate picture," he said.

On a personal level, Spurgin said he would not be comfortable being in a vehicle with someone at the wheel who had used marijuana.

"I've been doing traffic safety research now for about three years and it's really helped open my eyes," he said. "Any substance, or any sort of impairment - even if its drowsiness or distraction - is going to prevent someone from driving to the best of their abilities."