When I was in high school I remember hearing about a test the CHP did (this was before the limit was dropped to .08) where they did a driving test after drinking. They did the test sober, then did it with 1 beer in the hour before driving, then tested with 2 beers, then 3 beers, and stopped at 4 beers. When sober the patrolman drove fine, with 1 beer he actually drove better than sober, with 2 beers he was back to about the same as sober, with 3 he started to make mistakes and with the 4th he did terrible.