We already have "Roadside Drug Testing" in Queensland/Australia, came into full force 12-18 months ago, alongside "Random Breath Tests" that have been in for decades.
They have a little square saliva tester, one side is Cannabis, the other side is Methamphetamine (includes MDMA metabolites also)... it's scraped facing downwards on your tounge and within 5 minutes will give a result.
The timeframe is generally ~6 hours for smoked cannabis, ~24 hours for methamphetamine and party drugs.
What are the penalties?
Any trace of illegal drugs in your system and the court may impose a fine of up to $1,050 and you could lose your licence for up to nine months for a first offence.
If you are found drug driving a second time while an outstanding drug driving offence is still to be heard by a court, you will have your driver licence suspended until the matter is heard or finalised by a court.
Be afraid
In all honesty, I was a toker/driver for the past 10 years, I have absolute faith in my driving skills while buzzing... but these roadside drug tests have stopped me
completely in my tracks, the penalty is far too large for me to handle.
Been roadside drug tested 3 times since it came into effect.