If only that were actually the law. My roads are 100% private with absolutely zero tax payer funding yet the dumbass registration laws and requirement to display a plate even apply on my private road (only exempt if the owner white-lists traffic, which cannot be done under my easement rules which at best would only might allow me to black-list abusers). In fact pretty much all the roads in my town are completely privately funded and privately owned yet you still need registration/plate along with the legal mumbo jumbo to obtain it.
Pretty soon you realize the laws have nothing to do with the fiction of the laws being there to protect the public roads or public land or taxpayer funding or some such, it's a sham pretense that falls apart upon inspection of how they work.