49 C.F.R. § 37.187
Example 1. By going to Operator X's ticket office or calling X for a reservation, a passenger can buy or reserve a ticket from Point A through to Point C, transferring at intermediate Point B to a bus operated by Operator Y. Operator X is responsible for communicating immediately with Operator Y to ensure that Y knows that a passenger needing accessible transportation or equivalent service, as applicable, is traveling from Point B to Point C. By immediate communication, we mean that the ticket or reservation agent for Operator X, by phone, fax, computer, or other instantaneous means, contacts Operator Y the minute the reservation or ticketing transaction with the passenger, as applicable, has been completed. It is the responsibility of each carrier to know how to contact carriers with which it interlines (e.g., Operator X must know Operator Y's phone number).
Example 2. Operator X fails to provide the required information in a timely manner to Operator Y. Operator X is responsible for compensating the passenger for the consequent unavailability of an accessible bus or equivalent service, as applicable, on the B-C leg of the interline trip.
Example 1. In Example 1 to paragraph (a) of this section, Operator X provides the required information to Operator Y in a timely fashion. However, Operator Y fails to provide an accessible bus or equivalent service to the passenger at Point B as the rules require. Operator Y is responsible for compensating the passenger as provided in § 37.199 .
Example 2. Operator X provides the required information to Operator Y in a timely fashion. However, the rules require Operator Y to provide an accessible bus on 48 hours' advance notice (i.e., as a matter of interim service under § 37.193(a) or service by a small mixed-service operator under § 37.191 ), and the passenger has purchased the ticket or made the reservation for the interline trip only 8 hours before Operator Y's bus leaves from Point B to go to Point C. In this situation, Operator Y is not responsible for providing an accessible bus to the passenger at Point B, any more than that it would be had the passenger directly contacted Operator Y to travel from Point B to Point C.
Example 1. Operator Y's office is staffed only during normal weekday business hours. Operator Y must have a means of receiving communications from carriers with which it interlines (e.g., telephone answering machine, fax, computer) when no one is in the office.
Example 2. Operator Y has the responsibility to monitor its communications devices at reasonable intervals to ensure that it can act promptly on the basis of messages received. If Operator Y receives a message from Operator X on its answering machine on Friday night, notifying Y of the need for an accessible bus on Monday morning, it has the responsibility of making sure that the accessible bus is there on Monday morning. Operator Y is not excused from its obligation because no one checked the answering machine over the weekend.
49 C.F.R. §37.187