(Disclaimer: I've only read all posts up to the quoted one. Sorry if I repeat something that was already said.)
Legitimate drunk driving has always been illegal. But how is "drunk" determined? The presence of alcohol, or so impaired that driving is obviously effected?
Most of us want drivers to be safe, but this can go too far, and we are already going down the road you want to take us. How many texting while driving incidents before life in prison? How about putting on make-up while driving? Shaving? Or how about the true number one cause of accidents, driving while tired?
And while we are at it, let's make getting a license a true test of competency. No more bad drivers on the road. No more beginner drivers on the road. No more drivers that come to complete stops in the fast lane of the freeway so they can slowly cut across all lanes of traffic to make an exit that they are missing.
And when you start down this path there is only one outcome: more draconian laws, more law enforcement, bigger budgets, and more people in jail. And in the end, the worse drivers on the road will probably still be out there, because you can't outlaw stupid.
The really interesting thing about those problems is, that the crucial point is not so much that the laws regarding driving are so bad, but rather the fact that the government shouldn't even be in the position to make these kinds of laws. It's first and foremost a property rights issue.
If roads were privately owned, as every good and service should be, the owner would have to decide whether there should be a driver's license required or not. Whether there should be a limit on the blood alcohol level and how high this should be. The same is true for speed limits, etc. And also, of course, for the fines for breaking these rules as well as there execution.
The entrepreneur would have to balance the additional revenue from drunk, speeding drivers against the lost revenue from all the people who seek alternatives to that road, because it would have an abyssmal death rate with a total laissez-faire policy. And I'm almost certain, that roads would be a lot safer in this system than today's roads, because that would have a much more beneficial impact on profits.
I also think that this is a good opportunity to criticize some libertarians who believe it's against the NAP for the government to enforce driver's licenses (which would, in some way, almost certainly exist in a private road system), etc. The government is the owner of the street. The owner choses the rules. There is nothing intrinsicly bad about that. The reason it's a mess is because the government owns the road (obviously bought with stolen money) and therefore no competition over the best set of rules for the marginal costumor of "driving" exists, because nobody is able to compete with a government that offers a service you have to pay for whether you use it or not.
The same principle is true for public education, health care, etc. As long as these things are publically owned, governments are going to make the rules. They are mostly going to be very bad rules, but democracy is a really bad way of determining what should be done instead. The way to sort these problems out is via free markets and competition.