N.Y.C. Admin. Code § 27-458: § 27-458 Ramps.

Vehicular ramps in public garages shall not exceed a gradient of one in seven, and their surfaces shall be nonslip. A landing having a minimum length of twenty feet shall be provided at the discharge point at the street level, within the street line. Ramps serving as required exits shall be enclosed in construction having a two hour fire-resistance rating except that openings for motor vehicles at each parking tier may be protected by a water curtain consisting of deluge-type sprinkler heads supplying at least three gallons of water per minute per linear foot of opening.