With recreational marijuana set to become legal on Oct. 17, police forces across Canada are stepping up efforts to train officers to detect drivers under the influence of the drug.

A new piece of legislation that changed Canada’s impaired driving laws gives police enhanced powers to conduct roadside intoxication tests, including oral fluid drug tests. Driving while high will remain illegal after legalization.

Public Safety Canada announced in September 2017 that it would invest up to $81 million in new law enforcement training to help officers weed out impaired drivers through a 12-step evaluation known as a drug recognition expert evaluation.

The test, according to Const. Chad Morrison, a drug recognition expert and drug evaluation and classification coordinator with Nova Scotia’s RCMP traffic services, helps detect “central nervous system depressants, inhalants, dissociative anesthetics, cannabis, central nervous system stimulants, hallucinogens and narcotic analgesics.”

Here’s what to expect if you are pulled over on suspicion of impaired driving:

At the roadside

After first using a breath test to rule out alcohol as the main cause of impairment, the officer will interview the driver and complete a pulse check. The driver will then be asked to complete three tests: an eye test, the one-leg stand, and the walk and turn.

Once the impaired driving legislation is enacted in December 2018, police officers will also be able to conduct roadside saliva tests.

At the police station

If, after the roadside tests, the officer finds probable grounds to believe the driver is impaired, they will take the driver back to the police station.

There, the driver will undergo a series of medical tests to rule out medical reasons for the suspected impairment. These include taking the driver’s blood pressure, temperature, and conducting a second pulse test. An examination of the driver’s muscle tone follows since some drugs may cause muscles to go limp or become rigid.

Next, the driver will face a series of more challenging tests, known as “divided attention tests,” which Morrison says “test your ability to divide your attention to multitask.” These tests include tilting your head back, closing your eyes, and then putting a finger to your nose. Another test involves raising a foot and looking at it while counting aloud.

The driver’s pupils will be examined again in both the light and in the dark, and the officer will search for and examine any injection sites.

If the officer still believes after the evaluation that the driver is impaired, they may ask the driver for a blood or urine sample to corroborate or dispute their findings.

The 12-step process takes 30 minutes to an hour to complete.

A report from May 2018 on cannabis and driving published by the Canadian Centre on Substance Use and Addiction and the European Monitoring Centre for Drugs and Drug Addiction noted that drug recognition evaluations are not foolproof.

“Outcomes of oral fluid screening and those from blood tests quite often do not match,” the report said.

It also added that the amount of THC—the primary psychoactive ingredient in cannabis—in blood or saliva “is not as strongly related to driver impairment as (blood alcohol content) is to alcohol-impaired driving.”

With a report from CTV Atlantic's Heidi Petracek.