Local authorities may by general rule, ordinance, or regulation exclude vehicles from any cemetery or ground used for the burial of the dead, or exclude vehicles used solely or principally for commercial purposes, from any park or part of a park system where such general rule, ordinance, or regulation is applicable equally and generally to all other vehicles used for the same purpose, if, at the entrance, or at each entrance if there be more than one, to such cemetery or park from which vehicles are so excluded, there shall have been posted a sign plainly legible from the middle of the public highway on which such cemetery or park opens, plainly indicating such exclusion and prohibition.