For all secondary transit-adjacent sites, the provisions of this Section are optional. On such sites, an optional transit volume may be provided in accordance with a determination by the transit agency and certification by the Chairperson of the City Planning Commission pursuant to Section 66-31 (Determination and Certification for Optional Transit Volumes). Where a transit volume is provided, special use, bulk, parking, and streetscape regulations are set forth in Sections 66-32 (Special Modifications for Secondary Transit-adjacent Sites).