As the federal government prepares to legalize marijuana, Mounties are being trained to spot drivers impaired by drugs.

Impaired driving is one of the leading causes of fatal crashes, resulting in roughly 65 deaths each year in B.C.

And the drug of choice isn't always alcohol.

Law enforcement agencies across Canada are now being trained to spot the signs of drug impairment, especially from marijuana.

"There's lots of training to be done," said Public Safety Minister Ralph Goodale.

"It will be very helpful to help officers make those roadside judgement calls."

Ottawa has allocated $274 million to the initiative, which is already underway in Vancouver. Officers are learning a 12-step system to spot the signs, including examining the eyes, testing attention span, and checking blood pressure and pulse.

There is currently no government-approved roadside testing technology for cannabis, but it is in the works. The RCMP and other agencies have been experimenting with more scientific approaches such as saliva tests.

Public safety advocates are applauding the training, and pushing for changes to impaired driving laws to give police new power—changes already proposed to Bill C-46, which are still before the Senate.

"The rates of drug-impaired driving are twice that of alcohol-impaired driving," said MADD Canada's Eric Dumschat.

According to the organization, about 15 per cent of fatal crashes in Canada in 2013 involved drivers positive for alcohol alone, while 28 per cent involved drugs alone. Another 16 per cent involved drivers positive for both.

MADD said of those fatal crashes, cannabis was present in almost half.

With marijuana on the verge of legalization, those rates could rise, advocates fear.

With a report from CTV Vancouver's Sarah MacDonald