What with all the fancy electronic gadgets popping up on vehicles these days, and the fact that they're pretty much all linked up to the engine management system, surely it wouldn't be too much trouble to install a device which could monitor the drivers breath and therefore it's alcohol level.
this device just above the drivers head, or even into the sun visor area. There are currently various hand held electronic breath testers available so the technology is obviously there. I reckon it wouldn't need to be any bigger than a small microphone, which would then be connected to the ignition system of the car.
Essentially what should happen is, jump into the car, insert key into the ignition, turn key.... and nothing happens. On the sat-nav display would be a message telling the driver that he/she is over the allowed alcohol limit and display a list of phone numbers of the local taxi companies.
Obviously this would only be available on new cars as retro fitting to older models would probably be cost prohibitive.
Many social problems such as this need to be addressed, by either the government, vehicle manufacturers, or the alcohol companies.
Or all of them working together. Now there's an idea....