Question:

In a libertarian society of limited government, and little interference in our everyday practices, what would govern our crowded highways if state and federal governments did not? Would we feasibly be able to operate a traffic system with out speed limits and DUI laws?

Answer:

Road owners, whether businesses or individuals, would decide how to operate their road, much as condominium groups do today. My guess is that reckless drivers would be targeted, rather than people going a few miles over the speed limit.

Some road owners might be stricter than our government with regards to drinking and driving. In a libertarian society where restitution was the norm, people would have even greater incentive to avoid causing an accident.