28 CFR Part 35 Title II Notice of Proposed Rulemaking (NPRM) (published 2008)

(ii) A path of travel includes a continuous, unobstructed way of pedestrian passage by means of which the altered area may be approached, entered, and exited, and which connects the altered area with an exterior approach (including sidewalks, streets, and parking areas), an entrance to the facility, and other parts of the facility.

(A) An accessible path of travel may consist of walks and sidewalks, curb ramps and other interior or exterior pedestrian ramps; clear floor paths through lobbies, corridors, rooms, and other improved areas; parking access aisles; elevators and lifts; or a combination of these elements.

(B) For the purposes of this section, the term path of travel also includes the restrooms, telephones, and drinking fountains serving the altered area.

(C)  Safe harbor.  If a public entity has constructed or altered required elements of a path of travel in accordance with the specifications in either the 1991 Standards or the Uniform Federal Accessibility Standards, the public entity is not required to retrofit such elements to reflect incremental changes in the proposed standards solely because of an alteration to a primary function area served by that path of travel.