Nev, I think what I am trying to say is (and, again, please dont take this as an argument for driving whilst under the influence) that there are several things that may impair a drivers' judgment (car stereo, tiredness, stress level, smoking, having a conversation, noisy children in the back) and having some alcohol in your blood is actually OK in that context. I dont mean over the legal limit, but I do mean that having a zero alcohol limit is not sensible. And the only way to ensure a zero alcohol level is to never, ever, drink alcohol if you are going to drive.
If you have one glass of wine (or a beer etc), how long afterwards would you say that you are safe to drive? Assuming 2 units per 'drink' and an average unit clearance of 1 hour, do you mean after 2 hours? Or do you mean after 12 hours? Or perhaps even 24 hours? Due to the way various substances are eliminated from the body, it is likely that 24 hours after a single 'drink' that there is still some alcohol detectable - would this mean you are an unsafe driver? Absolutely not.
I really dont want to get drawn into a prolonged discussion in this emotive topic, but the very reason it is emotive can sometimes reduce the amount of common sense applied. Using your argument then anybody with noisy children, a switched on car stereo, is tired (a significant cause of accidents and essentially impossible to quantify how 'tired' someone is, indeed how tired you are yourself), has had a bad day at work etc, well they shouldnt be driving either as they will have >1% cognitive impairment.
Nobody in their right mind would advocate driving above the legal limit, but to have an absolutely zero limit would, I think, not be sensible. At least until it becomes mandatory to self-check blood alcohol levels whenever drinking occurs.
Thanks,
Adam