Although the driver wasn't drunk, friends of ours were involved in a similar rear-end collision with a motorist in a Ford Expedition who was talking on the phone and drifted off-line into the rear end of their tandem.
http://www.tailwindtandemclub.com/Wear%20a%20mirror.htm
Helmets, mirrors, a working knowledge of the rules of the road, common sense, and situational awareness are all critical for anyone who rides their bicycle on public roads.