There's more to it that that, IMO. We send all kinds of mixed messages on this subject. One the hand, we send the message that you should never drink and drive but at the same time we see advertisement after advertisement showing happy people drinking at a party or happy people drinking at a bar etc. These places are away from home and the almost mythical designated driver can't drive every guest home.
We need a zero tolerance/zero consumption kind of thing. Legalize marijuana and apply the same rules to each. If you've consumed either within X amount of time, you go to prison for life. Take all the money we waste right now because of the war on drugs/criminalization of pot and have all the booze companies contribute their annual marketing allocation and you have more than enough money to provide free, effective alternatives to driving (cots in the back, taxis, transporters whatever). And yes, I'm only partially serious but until we can do something like this we will always have a drinking & driving problem.
Steve