The maximum permitted residential density shall be fourteen (14) dwelling units per acre of gross residential tract area within the AHOZ-2 Zone, except that if the developer elects to exercise the townhouse option permitted at subsection 37-44.3b, the maximum permitted residential density on the portion of the gross residential tract area devoted to the townhouse development shall be ten (10) units per acre, notwithstanding which the maximum permitted residential density on the remaining portion of the gross residential tract area to be devoted to multifamily (apartment) dwellings shall not exceed fourteen (14) units per acre. Land occupied by the cartway of and any center island(s) within the proposed access roadway, whether such roadway is to be used exclusively by the residential development or is to be used in common with other uses on the balance of the tract, shall be considered part of the gross residential tract area for the purposes of calculating density, but land proposed to be developed with the uses permitted in the G-B Zone shall not be considered part of the gross residential tract area. In addition, an accessory apartment for the sole purpose of housing the project superintendent may be constructed above any proposed maintenance garage, which unit shall not be considered for the purposes of calculating density.