Megan McArdle suggests a good idea for fighting drunk driving among teens:
[Institute] driver’s licenses for convicted DUIs that tell bartenders not to serve you. Combined with a zero tolerance policy, this would be a pretty effective deterrant to drunk driving for teens. Right now, groups of teens drink together, in secret. But if your friends can drink at a bar, and you can’t, you’ll find your social life dramatically curtailed. Teenagers are very sensitive to penalties that separate them from their friends. I’d lower the drinking age to 16, as in Europe, but require licenses to show that you haven’t had a DUI.