OTTAWA -- The Canadian Automobile Association is lobbying for a government-funded public education program to warn of the dangers of cannabis-impaired driving before Canada legalizes recreational pot.

Police will also need more funding to learn how to recognize and investigate drug-impaired drivers, says the CAA.

The Liberal government has promised to introduce legislation legalizing recreational marijuana next spring and a committee report on the process is expected at the end this month.

The CAA helped fund a study by the Ottawa-based Traffic Injury Research Foundation that suggests legalization will pose "incredible challenges" for managing pot-impaired drivers.

The study is sure to inflame the escalating propaganda war over marijuana's harms and benefits, because it is premised on the assumption that access to legal cannabis will increase traffic accidents.

The CAA commissioned a poll that found almost two thirds of respondents are worried roads will become more dangerous after legalization.

"There are a lot of misconceptions out there that marijuana doesn't affect your driving, or even worse, it makes you a better driver," Jeff Walker of the Canadian Automobile Association said in a release.

"There need to be significant resources devoted to educating the public in the run-up to, and after, marijuana is legalized."

A Conservative senator has introduced legislation that would give police the power to obtain oral swabs or blood samples from drivers to detect THC, the active intoxicant in cannabis.

But pot activist Jodie Emery says the presence of THC can be detected up to a month after use and doesn't indicate impairment.

"Of course I'm against impaired driving, but impairment is proven by performance," Emery said in an interview. "Police already have all the tools they need to detect impaired drivers on the road."

The CAA-funded study notes there is a lack of good research data on what it calls the "magnitude of the relationship between THC use and collision risk."

The automobile association release refers to the Canadian Centre on Substance Abuse, which in turn has cited a 2012 meta study of other research that concluded "Acute cannabis consumption nearly doubles the risk of a collision resulting in serious injury or death."

However a 2015 study by the National Highway Traffic Safety Administration -- which the U.S. government agency called "the most precisely controlled study of its kind yet conducted" -- found that marijuana smokers had only a minimally higher risk of being involved in a traffic accident than sober drivers. The 20-month-long survey of more than 10,000 drivers in Virginia Beach, Va., found no "significant increased risk of crash involvement" from cannabis use.

The largest population-based study, involving nine European Union countries in 2010, also found the traffic accident risk from pot impairment was "not statistically significant."

"Drivers positive for THC were estimated to be at elevated risk (1--3 times that of sober drivers)," said an NHTSA review of the research, while the same study found alcohol-impaired drivers had elevated crash risks of between 20 and 200 times that of sober drivers.

That's not to say the risk is zero.

"Performance deficits (for drivers) have been found in tracking, reaction time, visual function, concentration, short-term memory, and divided attention," says the 2012 research cited by the Canadian Centre on Substance Abuse.

But even though recreational marijuana is self-evidently an impairing substance, many Canadian youth aren't getting the message.

The CAA-commissioned poll of 2,102 Canadians, conducted by Earnscliffe Strategy Group, found that 26 per cent of respondents between the ages of 18 and 34 "believe a driver is the same or better on the road under the influence of marijuana."

The online poll claims a margin of error of plus or minus 2.2 percentage points, 19 times in 20, although the Market Research and Intelligence Association rules say online panels should not include error margins.

As the traffic foundation study observes: "the pervasive messages from pro-cannabis groups have made it more challenging for road safety messages to be heard."

A random sample of British Columbia drivers in 2013 found that 5.5 per cent tested positive for cannabis. And Health Canada reports that its 2012 Canadian Alcohol and Drug Use Monitoring Survey found that 2.6 per cent of drivers in Canada admitted driving within two hours of using cannabis at least once in the previous 12 months.

Cannabis has a half-life of about two hours in the human body, which further complicates police efforts to accurately measure drivers' THC levels in a timely fashion.

"To conclude, cannabis-impaired driving is complex and it will require a continuum of road safety strategies to complement the new legislative changes to cannabis regulation," states the Traffic Injury Research Foundation report.