Methinks you avoided answering the question. How do you solve the speeding conundrum? Provide a practical libertarian solution that would translate across the necessary legal system to support a large society.
"My right to go as fast on the highway as I want to ends exactly at the point where the speed at which I propel my vehicle on said highway interferes with your right to travel the same highway with an adequate assurance of safety."
'Tis hardly a conundrum.