That's the reasoning, but to me it just proves that drunk driving shouldn't be a crime separate from poor driving. (I guess it would be OK as an aggravating factor for other traffic crimes.) Someone who drives acceptably while drunk drives acceptably, period.
I figure the reason it's set up that way is because BAC is way easier to determine on the side of the road during a traffic stop than a comprehensive study of someone's driving, so we have to lean to the less permissive side.
(We opt not to lean to the more permissive side because drivers who are drunk are indeed already responsible for a great deal of injury, loss of life, and damage)
I don't know. You can't, unfortunately, stop everyone who drives poorly. Too many people do - and even if they just got off with points on their license, quickly enough they'd be banned and then out of work.
Seriously, I can drive for fifteen minutes and see dozens of people who are driving too close together or committing some other sin. All those people who, just going into a corner, you see lighting off their brakes one after another - when all you, a little further back, have to do is roll your toes back a little to take some of the speed out.
Considering random breath tests don't seem to be that big of a thing, (I think - https://www.askthe.police.uk/content/Q723.htm - that they can't do truly random testing,) they're probably picking the people liable to be the worst examples anyway. Which I suspect is the most we can practically hope for at the moment.
for better or worse, it's not far off. imagine we could cross reference some street level CCTV (license plate, maybe gate and facial recognition) and "select driver_dl from trips where driving_ability < 0.7"; revoke licenses from those who can't drive well, consistently... to pay for it, maybe, we could just issue some DUI tickets where the car was parked in-front of a bar for a while and the driver appeared to walk unusually (dozens of violations per habitual drinker, ez). cross reference some phone/text and CC metadata to determine sociability and spending, maybe more, and you can get a pretty good certainty who's probably driving under the infuence and/or a poor driver, and take them off the road.
barely fiction (maybe not at all?), but it won't be hard forever and they won't need to "stop" many people in the sense that is hard to do, for much longer.
