In all Commercial Districts, railroad or transit air space may be developed or used in accordance with the provisions of this Section.

1. Railroad or transit air space may be developed or used only for a permitted use accessory to the railroad or transit right-of-way or yard, a use permitted by the City Planning Commission as set forth in Section 74-61 (Development within or over a railroad or transit right-of-way or yard), or a railroad passenger station permitted by the Commission as set forth in Section 74-148 (Railroad Passenger Stations) unless the right-of-way or yard or portion thereof is no longer required for railroad or transit use as set forth in paragraph (b) of this Section.
   
   If any building or other structure constructed in such railroad or transit air space in accordance with the provisions of Section 74-61 is enlarged or replaced by a new building or other structure, the provisions of this Section shall apply to such enlargement or replacement.
   
   However, any use legally established in such railroad or transit air space in accordance with the provisions of Section 74-61 may be changed to another use listed in a permitted Use Group and no additional special permit from the Commission shall be required for such change of use.
   
   Any building or other structure within or over a railroad or transit right-of-way or yard, which building or other structure was completed prior to September 27, 1962, or constructed in accordance with the applicable provisions of Sections 11-31 to 11-34, inclusive, prior to December 5, 1991, may be enlarged or replaced in accordance with the applicable district regulations without any requirement for a special permit from the Commission. Ownership of rights permitting the enlargement or replacement of such a building or other structure shall be deemed to be equivalent to ownership of a zoning lot or portion thereof, provided that such enlargement or replacement will be on one block and the rights are in single ownership and recorded prior to February 22, 1990. Such ownership of rights shall be deemed to include alternative arrangements specified in the zoning lot definition in Section 12-10 (DEFINITIONS).
   
   Enlargement or replacement utilizing these ownership rights shall be deemed to be constructed upon the equivalent of a zoning lot.
2. When the use of a railroad or transit right-of-way or yard or portion thereof has been permanently discontinued or terminated and a large-scale residential or community facility development or a large-scale general development requiring one or more special permits is proposed, no use or development of the property shall be allowed until the Commission has authorized the size and configuration of all zoning lots on such property. As a condition for such authorization, the Commission shall find that:
   1. the proposed zoning lots, indicated by a map describing the boundaries of the total area of each lot, are not excessively large, elongated or irregular in shape and that no development on any zoning lot would result in the potential for an excessive concentration of bulk that would be incompatible with allowable developments on adjoining property; and
   2. each resulting zoning lot has direct access to one or more streets. 

No subsequent alteration in size or configuration of any zoning lot approved by the Commission shall be permitted unless authorized by the Commission. The Commission may prescribe appropriate conditions and safeguards to minimize adverse effects of such zoning lot designation on the character of the surrounding area. Such conditions shall be set forth in a written Declaration of Restrictions covering all tracts of land, or in separate written Declarations of Restrictions covering parts of such tracts of land and which in the aggregate cover the entire tract of land comprising the zoning lot, which is executed and recorded as specified in the definition of zoning lot in Section 12-10 (DEFINITIONS).

Prior to granting any zoning lot authorization relating to such right-of-way or yard, the Commission shall request the Metropolitan Transportation Authority and the Departments of Transportation of the State of New York and the City of New York to indicate within 30 days whether said agencies have any plan to use such property or portion thereof for a railroad or transit use.

1. Notwithstanding the above, the High Line, as defined in Section 98-01, shall be governed by the provisions of Section 98-16 (Air Space Over a Railroad or Transit Right-of-way or Yard).