Quebec is stepping up its fight against impaired and high-risk drivers with new, tougher rules that take effect today.

The changes to the province's highway traffic act includes a "three strikes, you're out" provision, which forces drivers caught over the legal blood alcohol limit three times to install an ignition interlock device to prevent the car from starting if they are impaired.

The new rules also target those behind the wheel of commercial passenger vehicles and heavy trucks.

Taxi drivers, bus drivers and anyone driving a minibus in Quebec will now face zero tolerance when it comes to blood alcohol.

Heavy truck drivers must now have a blood-alcohol level under .05 mg per 100 ml of blood.

The new limits don't apply to drivers of motor homes or those pulling campers.

The legal blood alcohol limit for all other drivers in Quebec remains unchanged at .08 mg.

High-risk driving behaviours

The changes to the law also mean stiff new penalties for anyone caught car surfing or street racing.

Car surfing – a stunt where people ride on the exterior of a moving car as if they were surfing a wave — has been widely condemned by police and safety authorities for the significant risk it poses.

Several people, mostly youths, have been seriously injured or killed in Canada in the past three years in car surfing incidents.

The new law makes it illegal to stand on the outside or the body of a vehicle or cling to it while in motion.

Police can now immediately seize a car for seven days if a driver is caught street racing or car surfing, or allowing someone to car surf on the vehicle. Offenders could face a $1,000 fine and demerit points.

"Street racing and car surfing are behaviors that are completely anti-social and dangerous," Transport Minister Pierre Moreau said a day before the changes came into effect.

"They must be condemned and cannot be justified in any way."

The new measures are the result of Bill 71, adopted in December, which also included the introduction earlier this year of a provision that limits drivers 21-years-old and younger from having any alcohol in their system.

Other notable amendments:

• Pedestrians are now prohibited from crossing an intersection diagonally, except where signs permit.
• Police can now immediately seize cars for 90 days if drivers are found impaired and previously had their licence cancelled for an alcohol-related offence or refused to give a breath sample in the last 10 years.