Any employee of the United States Postal Service, while actually engaged in depositing mail in mail boxes placed along a street or highway as defined in the traffic code, or while engaged in delivering and collecting mail therefrom, may permit the postal employee’s motor vehicle to stand unattended with the motor running; provided that such postal employee shall first effectively set the brakes thereon; and provided further, that when the motor vehicle is left standing unattended upon any grade the front wheels shall be turned to the curb or side of the highway. This section shall have no application where such employee leaves the highway for any purpose.
(Sec. 15-13.8, R.O. 1978 (1983 Ed.)) (1990 Code, Ch. 15, Art. 13, § 15-13.7)