49 CFR §37.187

1. (a)When the general public can purchase a ticket or make a reservation with one operator for a fixed-route trip of two or more stages in which another operator provides service, the first operator must arrange for an accessible bus, or equivalent service, as applicable, to be provided for each stage of the trip to a passenger with a disability. The following examples illustrate the provisions of this paragraph (a):
2. (b)Each operator retains the responsibility for providing the transportation required by this subpart to the passenger for its portion of an interline trip. The following examples illustrate the provisions of this paragraph (b):
3. (c)All fixed-route operators involved in interline service shall ensure that they have the capacity to receive communications at all times concerning interline service for passengers with disabilities. The following examples illustrate the provisions of this paragraph (c):