I know when I used to go out drinking I would always drive. Not so much the designated driver per se but just that I could never trust anyone else. The friends I would go out with usually didnt know when to stop and would barely be able to stand up let alone drive. Now, That is not to say I didnt drink, But I usually felt I knew my limit. I was one of those , "I'm not too drunk to drive, I'm fine." And typically I was fine.
One average night I was feeling perfectly fine after after leaving a club with 4 friends in the car and noticed another friends boyfriend down the street (who happened to be a cop). Drove up, started chatting, he asked me to take a look at something kewl in his squad car, as soon as we got to the back of the car he fiddlesticked my world up!!!! Damn near body slammed me to the ground (me fighting the whole way did nothing to improve my situation) handcuffed, face mushed into the pavement, knee to the shoulder blades then nice and calmly was given a lecture on drunk driving. After I calmed down and was uncuffed, he made me take a sobriety test. I passed the skills test (head back, hands out, touch your nose type stuff) but still scored a 1.8 BAC!!! That would have landed me an instant unavoidable DUI. Well that was my wakeup call. Now, I dont risk it. If I know I'm driving I never have more than one drink for the evening.