I don't know about your area, but where I live the police set up checkpoints along common routes home from popular bars/restaurants to catch drunk drivers. Drunk drivers get caught extremely often and many of them lose their licence for long periods of time.

This does not discourage drunk driving as much as you would think. It does remove a lot of the drunk drivers from the road by force, however.

MADD only worked in the sense that it made some mothers feel somewhat absolved of whatever guilt they felt for losing a child. Their statistical claims are quite ridiculous, though.

Edit: Claiming credit moreso than flawed statistics, although both are highly questionable.