This bill proposes to amend title 54, United States Code, to establish that State law will apply to the use of motor vehicles on roads located within a "System unit," which refers to units of the National Park System. It defines "off-highway vehicle" according to the State's definition and "road" as the main-traveled surface open to motor vehicles and administered by the Service. Specifically, the legislation mandates that the laws of the State where a System unit is situated will govern the operation of all motor vehicles, including off-highway vehicles, on these designated roads. Any violation of these applicable State laws within a System unit would be expressly prohibited under this new provision.