Wow, I'm actually surprised at the misunderstanding of things like blood alcohol levels and things like testing. ie. a couple hundred bucks for a unit
As far as when you are not good to drive, certainly some people's ability to drive is "impaired" at only 0.08. There are many factors that decide that, weight, tolerance, did you eat, pop meds, etc etc.
Please show me data that proves NO ONE can be impaired at 0.08!!! Impaired being not 100% as effective behind the wheel as when completely sober.
I'll save you the time, it does no exsist, therefore, like Eyebrock said, its up to legislators to decide where they should stick the "safe" limit. It would be impossible to decide on a case by case basis with calculating all the variables if someone at .08 is really too far gone. I'll tell you this my wife would be far gone at 0.08. I want to assure ALL impaired drivers are off the road. Not just the 85% (arbitrary number) who are over 1.0.
To argue its a real hardship to not drink and drive is an absurd argument.
The 0.05 - 0.08 warning and 24 hours suspension is in effect in only a few provinces (Manitoba for sure) and even then its left to officer discretion.