In the Urban Renewal Multiple Dwelling B (R) District, no premises except multiple dwellings shall provide space for more than four motor vehicles. Not more than one commercial vehicle shall be allowed on premises developed for a one- or two-family house; the capacity of such commercial vehicle shall be limited to 3/4 of a ton or limited to a cubical capacity, including the driving compartment, not in excess of 160 cubic feet. On premises developed for multiple dwellings, no commercial vehicle shall be allowed.