Some ADA rules:
4.10 Elevators.
4.10.1 General. Accessible elevators shall be on an accessible route and shall comply with 4.10 and with the ASME A17.1-1990, Safety Code for Elevators and Escalators. Freight elevators shall not be considered as meeting the requirements of this section unless the only elevators provided are used as combination passenger and freight elevators for the public and employees.
4.10.2 Automatic Operation. Elevator operation shall be automatic. Each car shall be equipped with a self-leveling feature that will automatically bring the car to floor landings within a tolerance of 1/2 in (13 mm) under rated loading to zero loading conditions. This self-leveling feature shall be automatic and independent of the operating device and shall correct the overtravel or undertravel.
ASME A17.1-1990, Safety Code for Elevators and Escalators
ADAAG 4.10.1 requires that elevators meet the ASME A17.1-1990 Safety Code for Elevators and Escalators. Platform (wheelchair) lifts under ADAAG 4.11.2 must meet Section XX of this code, the Safety Standard for Platform Lifts and Stairway Chairlifts. (Note: More recent versions of the ASME A17.1 Safety Code do not include provisions contained in Section XX for platform lifts; these provisions are now provided in a new separate standard known as the ASME A18.1-1999 Safety Standard for Platform Lifts and Stairway Chairlifts.) For more information, contact: