The provisions of Section 28080 shall not apply to either of the following:
(a) Any motor vehicle upon which a camper is mounted if a person is able to move between the cab portion of the motor vehicle and the camper.
(b) Any motor vehicle upon which a camper is mounted, which motor vehicle is equipped with a sliding or removable rear window which can be opened or removed by a person inside such camper.
(Added by Stats. 1973, Ch. 292.)