Any required open space on a zoning lot which includes designated open space is subject to the special regulations set forth in Section 107-22 (Designated Open Space).

For buildings containing residences on zoning lots that include designated open space, driveways, private streets, open accessory parking spaces or open accessory off-street loading berths may occupy not more than the area set forth for the following districts:

(a)        in R1, R2, R3-1, R3-2 and R4 Districts, not more than 50 percent of the required open space not within the designated open space; or

(b)        in R3A, R3X, R4A and R4-1 Districts, not more than 50 percent of the lot area not occupied by buildings containing residences and not within the designated open space.

However, in all districts, a greater percentage may be so occupied if authorized by the City Planning Commission in accordance with the provisions of Section 107-661 (Modification of permitted obstructions).