There will be threshold levels just as there are for that other drug, alcohol, to account for a drug being in your system but not of a sufficient level to cause you to be impaired, and you can request an evidential blood test if you want to argue the toss.
The police already have a test for drug-impaired drivers. I thought it was an urban myth, but they can and do ask dodgy drivers to walk a straight line and stand on one leg to ascertain their level of impairment.
They also ask them how long they think 30 seconds is. Apparently this is a very effective test. Of those drivers they fail, who then go on to ask for blood tests, more than 90 per cent are found to be over the limit for drugs and/or alcohol.
However, the coordination tests are time consuming and require specially trained police officers - hence the saliva tests.
It seems incredible that we need laws to punish people who are incapable of driving. Surely, as sentient beings with IQ levels higher than rocks, we know that driving under the influence, whatever that influence might be, is endangering ourselves and innocents who happen to be sharing the road with us.
But humans are funny creatures. I had many talkback callers and texters tell me that they did not condone drug driving.
However, they did it.
They'd smoke a joint and drive home through the back roads and insisted it made them better drivers, because they drove slowly and they were mellow.
It reminds me of the olden days, when most people drove with a skinful and decried the new drink-driving laws.
They were adamant that driving under the influence of alcohol made them better drivers – they were more vigilant. They were hyper aware. And closing one eye enabled them to see the white lines more clearly.
Yeah, right.
Drinking and driving is not cool and nor is drugging and driving. I'm horrified thinking of the risks I took when I was younger and the world was a different place.
I will be forever grateful for being convicted for drink-driving 30-odd years ago, because a) I learnt my lesson without hurting anybody and b) I understood what a responsibility it is to be on the road, driving a vehicle.
We have a place up north, and it's a three and a-half hour drive to get there on a good day. And every time, I approach that drive like it's an Olympic event.
I don't drink for a few days before hand. If I've had a bad night's sleep, I postpone the weekend.
When I do head up, I stop a couple of times on the way to reset and refocus.
I'm well aware that I have a responsibility to others to be the safest driver I can be, and I have to be hyper vigilant for those who have yet to have learned their lesson.
Perhaps the best thing about the roadside drug testing bill is that it is a line in the sand. A shift in attitude.
Thanks to the enforcement of the drinking and driving laws, nobody thinks it's okay to get behind the wheel with a skinful.
With the introduction of the roadside drug testing, maybe people will also accept that driving under the influence of any drug is breaking the social contract we have with each other.
