When a building contains more than one occupancy and separate entrances are provided for individual occupancies, there shall be a main front entrance for each such occupancy, and a separate frontage space shall be provided for each main front entrance, except that a second frontage space is not required for a two-family Group R-3 occupancy if unobstructed access, 5 feet (1524 mm) in width, is provided to the rear yard and to the main front entrance of any dwelling unit from either side of the building that is not directly accessible from the public street, fire apparatus access road, or driveway. An open accessory parking area not less than 5 feet (1524 mm) in width shall be sufficient to constitute unobstructed access to the rear yard, regardless of the presence of parked vehicles in such parking area.