mikewint
Captain
Gumbyk, My assumption would be that on our interstate system the overall speed limit is 70mph(113kph) which generally means most vehicles travel at 80mph(129kph). In addition the interstate system is heavily used by trucks some of which gross 80,000 lbs(36,364kg). I suspect the feeling is that small light weight under-powered motorbikes would not be able to maintain traffic flow rates and would be swept off the road as a large truck passed