(1) A vehicle engaged in delivery of United States mail may be equipped with a blinker-type or revolving amber light mounted on the top of the vehicle, and the light may be illuminated while the vehicle is engaged in delivery of mail.
(2) A person delivering the United States mail and illuminating an amber light on a privately owned motor vehicle shall carry attached to the motor vehicle an identification card showing the name of the owner of the vehicle and signed by the postmaster authorizing the use of the amber light.