Your argument isn't valid because without taxation there would be no public roads to trespass on. At least not federally.

And there are other solutions:

- Tax property owners to pay for roads near their buildings

- Toll roads

- Private ways (actually very common in housing developments and usually work even better than public ones because the landlord / homeowners association is incentivized to keep them well taken care of to keep people from moving out)

- Local income tax (something most libertarian's aren't against because living in a locale is a choice that is easier to change than, say, what country you are a citizen of)

- etc

An interesting mental trap people fall into is thinking that because currently something is paid for one way that taking away that source of income will mean it won't be paid for. The market has a way of working things out.