it is illeagle to operate any slow vehicles on INTERstate hiways [ie, I40, I70, I80 ect] in the whole US, in most states it is leagle to operate tractors ect on INTRAstate hiways, [ ie us 30 us 70 as well as other state hiways, i live by a 4 lane hiway [ us 70] tractors, combines, road construction machinery are routinly driven on the hiway to where they're working, and almost every day we have full size backhoes driven upwards of 50 miles one way to a job, these are owned by a certain group of people who while they can buy the equipment, they can never seem to come up with a truck and trailer to haul them on, these are sometimes driven right by a dot inspection point for trucks near here, they dont seem to have a problem with the tractors at all