In Norway drink/driving and drug/driving are very socially unacceptable, and so those who do it tend to be 'outlaws on the edge of society', so they're crashing for other reasons, not just booze/pot.
So in short, the Norwegians understand that substance abuse is a symptom, rather than a cause of criminality. Seems in NZ and other New World Anglophone nations, anything other than attacking the symptom is too small to fit on a bumper sticker and shot down as "PC gone mad".
shot down as "PC gone mad"
this Allied Licker shotgun is superb
Any chance you have a link or citation for the Canadian study on fatal crashes? An odds ratio of 40 sounds quite close to 5*8 (odds for cannabis * odds for alcohol), suggesting that either no interaction was included in the model, or that the interaction was small or non-significant, which would be an interesting result.
I had a second think about this, and I don't think it can just be a multiplier. Example:
If for any drive you have a 1% chance of an accident. If cannabis makes that 5 times more likely, you have a 5%. Alcohol makes it 8 times more likely so that's 8%.
To figure out the multiplier of the two, you don't multiply 5% by 8%. You multiply 1-n. So that's 95% by 92%. Which is 87.4% - your chance of not having an accident while under both. Under a multiplier with a base of 1% you have a 12.6% of having an accident while under both.
That's 12.6 times as likely, not 40 times as likely.
If you redo it with a base of 0.1% (probably much more accurate, you have an accident every thousand times you drive), 99.5% times 99.2% = 98.7%. 1.3% chance of being affected by both, so 13 times as likely (there's some rounding taking place there).
So it's either incredibly basic maths fail, or there's something else going on.