36 CFR Part 1192 Americans with Disabilities Act (ADA) Accessibility Guidelines for Transportation Vehicles (2016 Non-Rail Vehicle Guidelines)

T502.4 Doorways with Steps on Over-the-Road Buses.

On over-the-road buses, doorways with steps shall provide an opening with a clear width of 30 inches (760 mm) minimum.

Exceptions: 1. The door opening clear width above a height of 48 inches (1220 mm) measured from the lowest step tread shall be permitted to taper so as to reduce in width to 18 inches (457 mm) minimum.

2. Where compliance with T502.4 is not structurally feasible, the door opening clear width shall be permitted to be 27 in (685 mm) minimum.

3. Hinges and other door mechanisms shall be permitted to protrude 4 inches (100 mm) maximum into the door opening clear width at or below 48 inches (1220 mm) in height measured from the lowest step tread.