Like all drugs, cannabis has effects on the brain that affect driving. It causes a decrease in vigilance and concentration, slower reflexes, poor coordination, longer reaction times, and impaired judgment.
When driving under the influence of cannabis, you could:
Police officers are trained to detect drivers who are “high” regardless of what they've taken.
Unlike with drinking and driving, police officers do not use a device to detect how much drugs you have taken. Rather, they will have you go through a series of tests by the side of the road in order to determine your ability to drive.
The police officer will have you follow a pen with your eyes in order to detect the presence of nystagmus (involuntary, jerky eye movements).
The police officer will ask you to walk on a straight line and turn around.
The police officer will ask you to keep your balance while standing on one leg and counting out loud.
While these tests may appear banal, they are difficult to pass if you are under the influence of drugs. If you fail these tests, the police officer will arrest you and take you to the police station where you will have to undergo other tests.
These are police officers who conduct another series of more extensive tests at the police station.
Among other things, they will measure or examine:
You will also be required to provide a sample of a bodily substance (e.g. urine).
You can be arrested and convicted under the Criminal Code if your driving ability is impaired by drugs, even if you haven't had a drop of alcohol. The penalties are the same as those for alcohol-impaired driving:
Combining drugs and alcohol greatly increases your risk of a car accident. It makes an explosive cocktail that has a huge impact on your driving by multiplying the effects of all substances involved.