(4) In ships having superstructures on the freeboard deck or superstructure decks,
which are open at either or both ends to wells formed by bulwarks on the open
decks, adequate provision for freeing the open spaces within the superstructures
shall be provided.
The minimum freeing port area on each side of the ship for the open
superstructure (As) and for the open well (Aw), shall be calculated in accordance
with the following procedure: