(a) General rule
With respect to alterations of an existing facility or part thereof used in the provision of designated public transportation services that affect or could affect the usability of the facility or part thereof, it shall be considered discrimination, for purposes of section 12132 of this title and section 794 of title 29, for a public entity to fail to make such alterations (or to ensure that the alterations are made) in such a manner that, to the maximum extent feasible, the altered portions of the facility are readily accessible to and usable by individuals with disabilities, including individuals who use wheelchairs, upon the completion of such alterations. Where the public entity is undertaking an alteration that affects or could affect usability of or access to an area of the facility containing a primary function, the entity shall also make the alterations in such a manner that, to the maximum extent feasible, the path of travel to the altered area and the bathrooms, telephones, and drinking fountains serving the altered area, are readily accessible to and usable by individuals with disabilities, including individuals who use wheelchairs, upon completion of such alterations, where such alterations to the path of travel or the bathrooms, telephones, and drinking fountains serving the altered area are not disproportionate to the overall alterations in terms of cost and scope (as determined under criteria established by the Attorney General).

(b) Special rule for stations

(1) General rule
For purposes of section 12132 of this title and section 794 of title 29, it shall be considered discrimination for a public entity that provides designated public transportation to fail, in accordance with the provisions of this subsection, to make key stations (as determined under criteria established by the Secretary by regulation) in rapid rail and light rail systems readily accessible to and usable by individuals with disabilities, including individuals who use wheelchairs.

(2) Rapid rail and light rail key stations

(A) Accessibility
Except as otherwise provided in this paragraph, all key stations (as determined under criteria established by the Secretary by regulation) in rapid rail and light rail systems shall be made readily accessible to and usable by individuals with disabilities, including individuals who use wheelchairs, as soon as practicable but in no event later than the last day of the 3-year period beginning on July 26, 1990.

(B) Extension for extraordinarily expensive structural changes
The Secretary may extend the 3-year period under subparagraph (A) up to a 30-year period for key stations in a rapid rail or light rail system which stations need extraordinarily expensive structural changes to, or replacement of, existing facilities; except that by the last day of the 20th year following July 26, 1990, at least 2/3 of such key stations must be readily accessible to and usable by individuals with disabilities.

(3) Plans and milestones
The Secretary shall require the appropriate public entity to develop and submit to the Secretary a plan for compliance with this subsection—

(A) that reflects consultation with individuals with disabilities affected by such plan and the results of a public hearing and public comments on such plan, and

(B) that establishes milestones for achievement of the requirements of this subsection.