Racin tires sound like fun. That old alchohol 5 hp racing cart I have does 70 mph.No kidin.
I would have to say no in the US but check your Dept of Motor Vveeeehickle. Those things are not seen by anybody on the road and fit nicely under any truck.
Why would you want to anyway they get stuck on any high part in the road and forget drivin in the rain or snow.
But it does sound like it could be fun, if we all had em.
I have seen some people who would drive around their dune buggy on the road, maybe that is what your looking for. Also your right, if we all drove go-karts it would solve a lot of problems...
ive seen golf carts with licence plates on them, other than that, its best to contact your local police station, things vary from one area to another, and if its not leagal in your area, im sure they would know. you could try the local D.M.V. but my experiance with them is that they are too busy to answer thier own phones, and dont much like to chat while doing work.