(1) A person commits the offense of violation of posted parking restrictions on state highways if appropriate signs or markings are posted giving notice of any regulations, restrictions or prohibitions on the parking, stopping or standing of vehicles on a state highway and:

(a) The person parks, stops or stands a vehicle on a state highway in violation of any such regulations, restrictions or prohibitions; or

(b) The person is the owner of an unattended vehicle parked on a state highway in violation of any such regulations, restrictions or prohibitions.

(3) It is an affirmative defense to a prosecution of the owner of a vehicle under subsection (1)(b) of this section that the use of the vehicle was not authorized by the owner, either expressly or by implication