New York Laws
Title 2 - Fire Protection and Safety
51-B - Mirrors in Connection With Self-Service Elevators.

ยง 51-b. Mirrors in connection with self-service elevators. In all
multiple dwellings in which there are one or more self-service passenger
elevators, there shall, pursuant to such regulations as the department
shall prescribe, be affixed and maintained in each such elevator a
mirror which will enable persons prior to entering into such elevator to
view the inside thereof to determine whether any person is in such
elevator.