What's wrong with the good old alcotest in front of the pub?
You know, actual policeman looking out for drunks and asking them how they get home, then offering to do a test right here to find out if they are over the limit before anything bad can happen. They can just ignore car-sized groups where one is obviously sober and looks like the DD.
They sometimes do it in Germany in front of discotheques and it's usually well received. Most people don't want to be driven by a drunk and a lot of people just overestimate what they can have and still stay under the limit. Few people/groups actually find drunk driving cool while they are sober.
Another successful move was mobile driving simulators. One driving school ever offered real tours while drunk to teach people they cannot drive as good as when sober. Technically, the instructor is the driver, so the student may be intoxicated and still suffer no penalty.
Mines the one with the car keys. I don't drink anymore, since I found better things to do with my brain.