(a) No operator of a vehicle shall stop, stand or park a vehicle for a period of time longer than is necessary for the expeditious loading or unloading of passengers in any place marked as a passenger zone.
(b) No operator of a vehicle shall stop, stand or park a vehicle for a period of time longer than is necessary for the unloading and delivery or pick up and loading of materials, in any place marked as a loading zone. In no case shall the stop for loading and for unloading of materials exceed thirty minutes.