Many people are underestimating marijuana's effects on motorists, the Canadian Automobile Association is warning.

CAA Atlantic spokesman Gary Howard told CBC News Wednesday there are many misconceptions about how marijuana affects driving.

Some people "believe that they can drive the same or better on the road if they're under the influence of marijuana," he said. "This is simply not true."

Education is key

The CAA says it has met extensively with the federal government in hopes the Liberals will put aside money for public education campaigns about marijuana. The government has said it will introduce legalization legislation next spring.

"Public education is critical here," Howard said. "We have to get ahead of this before it hits the street, so to speak."

The CAA also hopes there will be "clear and meaningful" laws to discourage Canadians from driving while under the influence of marijuana.

The group warns that public education and provincial drugged-driving policies will both take time, and that training police officers about drugged driving will have "substantial" costs.

Double the risk

The Canadian Centre on Substance Abuse says using marijuana before driving doubles the risk of being involved in a crash.

Doug Beirness, a senior research associate with the centre, specializing in impaired driving, told CBC Radio's Maritime Noon that making it clear marijuana and driving don't mix is the priority.

"The use of cannabis is inconsistent with a safe operation of a motor vehicle and the sooner that we accept that universally the better off we'll be," he said.

He said that doesn't necessarily mean zero tolerance, but he believes the legal limit should be quite low.

"Whether you issue criminal sanctions at that point or whether you do roadside suspensions as we do with alcohol and leave criminal sanctions for more egregious behaviour, that's up to Parliament," he said.

No marijuana breathalyzer yet

Beirness said part of the difficulty is that marijuana is less consistent in its effects on individuals than alcohol, making setting a limit trickier.

He said marijuana tends to impair users cognitively as opposed to physically, but that it's similar to alcohol in how it affects the driver's ability to stay in their lane.

He also says the technology isn't in place yet to have a "magic box" that would work for marijuana use the way a breathalyzer works for alcohol.

"At best, what we'll be able to do is use some kind of a screening device, probably based on oral fluid, that will tell us whether or not a person has recently used cannabis."

Then the police officer would have several options, he said, including a field sobriety test, a more formal evaluation "downtown" by a drug recognition expert or a roadside suspension.

With files from Maritime Noon and Krystalle Ramlakhan