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

T502.2 Doorways with Lifts, Ramps or Bridgeplates.

The vertical clearance at doorways with lifts, ramps or bridgeplates shall comply with T502.2. Vertical clearance shall be measured from the inside finished edge of the door opening to the highest point of the deployed lift, ramp or bridgeplate below.

T502.2.1 Over-the-Road Buses.

For over-the-road buses, the vertical clearance at doorways shall be 65 inches (1650 mm) minimum.

T502.2.2 Other Vehicles.

For other non-rail vehicles, the vertical clearance at doorways shall be 56 inches (1420 mm) minimum on small non-rail vehicles and 68 inches (1725 mm) on large non-rail vehicles.