The provisions of this chapter regulating the operation, parking and standing of vehicles shall not apply to vehicles operated by the police or fire department, any public ambulance, or any public utility vehicle or any private ambulance, which public utility vehicle or private ambulance has qualified as an authorized emergency vehicle, when any vehicle mentioned in this section is operated in the manner specified by the Vehicle Code in response to an emergency call. In addition, the provisions of this chapter regulating the parking or standing of vehicles shall not apply to any vehicle of a city department or public utility while necessarily in use for construction or repair work or any vehicle owned or operated by the United States Post Office Department while in use for the collection, transportation or delivery of United States Mail. The foregoing exemptions shall not, however, relieve the operator of any such vehicle from the obligation to exercise due care for the safety of others or the consequences of his wilful disregard of the safety of others. (Ord. No. 938, § 1.)