Commercial parking expansion. Upon obtaining special permit approval from the Board of Appeals, accessory automobile parking only at and/or below grade only shall be permitted. Full screening shall be provided on any residentially utilized sides of such lot, including the street frontage of the CX District in accordance with the provisions of this chapter. All permitted parking is to be an accessory use to a permitted use located within an abutting C-1, C-2 or C-3 District only, and all entrances and exits from such parking area shall be through abutting C-1, C-2 or C-3 District lots. All vehicular traffic entering or exiting such parking area shall flow to or from a C-1, C-2 or C-3 District and shall be directed away from any R District.