I’m not sure bridge designers are always following the guidelines of the Americans with Disabilities Act (ADA). But to be fair to designers the rules are not always clearly defined.
A proposal by the “Architectural and Transportation Barriers Compliance Board”, has been published, proposing accessibility guidelines for the design, construction, and alteration of pedestrian facilities in the public right-of-way.
The main guidelines for bridge designers seems to boil down to a few essential rules.
Minimum of 1.2 m (4′-0) wide, for lengths under 61 m (200′-0). Where the clear width of pedestrian access routes is less than 1.5 m (5.0 ft), passing spaces shall be provided at intervals of 61 m (200.0 ft) maximum. Passing spaces shall be 1.5 m (5.0 ft) minimum by 1.5 m (5.0 ft) minimum.
Most states are using a minimum 1.5 m (5′-0) sidewalk the entire length of the bridge.
R302.6 Cross Slope. Except as provided in R302.6.1 and R302.6.2, the cross slope of pedestrian access routes shall be 2 percent maximum.
R302.5 Grade. Except as provided in R302.5.1, where pedestrian access routes are contained within a street or highway right-of-way, the grade of pedestrian access routes shall not exceed the general grade established for the adjacent street or highway. Where pedestrian access routes are not contained within a street or highway right-of-way, the grade of pedestrian access routes shall be 5 percent maximum.
Most states are limiting grade to a 5% maximum for sidewalks.
Joints – big issue in bridges, usually you have to keep them small or cover them with a ADA approved plate.
R302.7.2 Vertical Surface Discontinuities. Vertical surface discontinuities shall be 13 mm (0.5 in) maximum. Vertical surface discontinuities between 6.4 mm (0.25 in) and 13 mm (0.5 in) shall be beveled with a slope not steeper than 50 percent. The bevel shall be applied across the entire vertical surface discontinuity.
Is there a similar document in other counties?