Zero tolerance to be Quebec's approach to weed behind the wheel?

It looks as though Quebec may adopt a zero tolerance approach to driving while high once cannabis becomes legal in Canada next summer.  

La Presse reports that Quebec intends to use THC levels in saliva as the yardstick for determining whether pot has been consumed.  Unlike THC levels in the blood, which can linger for days, THC is eliminated from saliva much more quickly.  Zero tolerance would therefore mean that motorists would have to put off driving for between four and six hours after consuming cannabis.  

The La Presse report says the zero tolerance for pot rule would apply to all drivers, not just those under the age of 21.