49 CFR 1312.16 - Substitution of service.
If a water or motor carrier (hereafter referred to as Carrier A) desires to have the option of substituting the services of a carrier of a different transportation mode (hereafter referred to as Carrier B) for part of its movement of a shipment, it may do so if:
(a) The shipment moves on the bill of lading that would be used if Carrier A were performing the service;
(b) Carrier A assumes the responsibility for the lading while it is in the possession of Carrier B; and
(c) Movement of the lading has been made prior to, or will be made subsequent to, the service performed by Carrier B.