For yourself, it just seems simpler to me to have a don't drink at all policy if you are going to drive. That am I over the limit bit is a hassle and makes for half assed thinking. Got to be firm about it with yourself, minimal thought required, that's all. I've busted some people's chops that were drinking and i didn't like the maneuvers when I was riding home at night or something. Catching up with them I smelled it. One guy was in his driveway by then, or i wouldn't have hesitated to hold and turn him in. Just go kill himself and I wouldn't sweat it, but also obviously not in a safe to other's state.