Researchers at the MUHC have determined that drivers who use cannabis are more likely to get into a crash for at least five hours after use.

The study looked at 45 people under the age of 25 who took part in driving simulation tests before and after getting high.

The result was that people were more likely to crash after using marijuana, whether tested one, three, or five hours after they used cannabis.

Study participants showed they were mostly able to drive in a straight line and maintain a steady speed but had a lot of difficult safely driving through intersections, changing lanes, and avoiding pedestrians.

The majority of study participants indicated that they would not trust each other to get behind the wheel within five hours of using a small dose of cannabis.

Study co-author Isabelle Gelinas said subjects felt less confident about their driving skills and drove more cautiously after using marijuana, but still failed routine driving tasks.

"Some of the more complex cases were that they had to drive on the road and something suddenly appeared in front of them and they had to avoid it to prevent crashing into the obstacle. They had a very busy intersection that was presented to them with cars coming on either side, and they had to cross, so they had to make a decision as to when it was a safe time to cross without getting into accidents," said Gelinas.

Drivers concerned about other motorists being high should focus on defensive driving skills, CAA chief strategy officer Jeff Walker told CTV News Channel on Monday.

"The best advice I can give is to make sure that we’re always driving safely. That’s the best path," he said.

The study was conducted by the Research Institute of the McGill University Health Centre and funded by the Canadian Automobile Association.

Second study looks at drivers who admit driving while high

Second study looks at drivers who admit hitting the road while high

A study by Université de Montreal researcher Jacques Bergeron found cannabis users who drive after getting high generally dismiss the effects of marijuana use.

That study found those who drove while impaired:

  • used cannabis more often
  • had friends who drove after using cannabis
  • were more likely to take risks

Recreational use of marijuana becomes legal in Canada on Wednesday but driving while impaired is banned, and Quebec has a zero-tolerance law regarding cannabis use and driving.

Police will be using a combination of saliva, blood, and urine tests, in addition to field sobriety checks to determine if drivers are impaired.