The last post shows what the problem can be. Most people don't think they are too drunk to drive and that their driving is just fine even though I have it on tape how poorly they were driving. If you are under the influence of intoxicants whether that be .04 or .15 your driving abilities and fine motor skills are lessened although not as severely at .04 is it would be at .15. It really doesn't matter how much further they have to drive, they shouldn't be driving at all.
Also, it doesn't matter how fast your metabolism is. Alcohol is burned at a constant rate by everyone and that is .015% per hour. It doesn't matter if you are drinking ocoffee or taking a cold shower.