The night I graduated from art school I went to a party with my boyfriend at the time and a few of his friends. At this point in my life I drank even more rarely than I do now, but I decided since it was MY graduation night, I wanted to have a few.
I asked my boyfriend, who always drank, if he would be the designated driver. He reluctantly said yes. Then the party he changed his mind and passed the duties to one of his friends.
On the ride home, we turned onto the [empty, traffic-free] highway and I realized something was very wrong. I looked around me and noticed to my utter horror that we were riding on the wrong side of a four lane highway. I calmly (??) pointed this out to my idiot ex boyfriend and his "sober" friend and we got off before we were killed or pulled over.
It turns out my boyfriend's friend was completely drunk, and had almost killed me soon after my 20th birthday. Delightful. Even when I think about it now it makes me queasy.
NEVER AGAIN did I trust my boyfriend (or anyone else in Pittsburgh) to be the designated driver. I ended up basically not drinking for the next 5 years.