Except for equipment and vehicles operated by a public authority or public utility, and except as otherwise provided below, the presence of any piece of construction machinery or other equipment, dump truck, garbage truck or other heavy truck of a type not ordinarily used as a means of transportation for people exceeding 500 pounds gross weight ("heavy equipment") is prohibited in all Farming and Residential and Professional zones, whether or not used or owned by an occupant of the lot. Such heavy equipment, when parked or stored in other zones, and all operable motor vehicles used on farms which are parked or stored outdoors, shall be screened from the street and adjacent residentially and professionally zoned property.