You've no doubt heard that the Government has proposed reducing the drink-driving limit from 80mg to 50mg following a review by Sir Peter North. Many years ago, a young woman whom I was acquainted with was killed when a drunk driver ploughed into her car. This was a terrible and unnecessary tragedy, but the point here is that the driver was drunk; he was well over the limit. He had not been carefully nursing a couple of pints all night.
Fatal alcohol-related accidents almost always involve drivers who have completely ignored the current limit, so they're hardly going to care about a lower one, especially as they know they are unlikely to be caught anyway. This measure is just an example of appearing to do something about a problem, but in reality doing absolutely nothing at all.
The way to deal with drunk driving is to increase the chances of being caught, which are extremely low, especially now that traffic police have largely been replaced by speed cameras. I would propose large-scale random breath tests carried out without warning, perhaps occasionally blocking off the entire town centre at night and breathalysing every driver. Yes, this may cause hold-ups, but it would greatly increase the chances of being caught drunk behind the wheel, thus creating the real deterrent that we don't have now. We should enforce the current law far more rigorously and not introduce one that drunk drivers will still ignore, but which penalises the careful driver who conscientiously drinks within the present limit.
P.S. (added 17 March): there's a saying that what's seldom is wonderful. In this case, it's me agreeing with a Tory. I've just read that Tory transport spokesperson Theresa Villiers said her party wouldn't cut the limit: “We do not believe the case has been made to justify such a change. We would focus on enforcement of the current rules.” The problem here is that if this issue becomes a party political battle, "New" Labour will never back down on principle - can't be seen to be yielding to the enemy, even if they're right (at least on this one point).