Parking of commercial vehicles in residential zones. One registered commercial vehicle of a rated capacity not exceeding two tons with two axles, owned or used by a resident of the premises, shall be permitted to be regularly parked or garaged on a lot in any residential district, provided that such vehicle is parked in a side or rear yard area, which area is relatively unexposed to neighboring properties and is screened from neighboring properties by plantings at least five feet in height. For purposes of this title, a commercial vehicle is a bus and/or vehicle containing advertising matter intending to promote the interest of any business, whether or not such vehicle is registered as a commercial vehicle with any State Division of Motor Vehicles; except that passenger vehicles which are commercially registered are exempt from these restrictions and, provided further, that this provision shall not be deemed to limit construction equipment which is used on the site for construction purposes.