48 CFR §47.305-15

1. (a)
   1. (1)Contractors are responsible for loading, blocking, and bracing carload shipments as specified in standards published by the Association of American Railroads.
   2. (2)The contracting officer shall insert in solicitations and contracts the clause at 52.247-58, Loading, Blocking, and Bracing of Freight Car Shipments, when supplies may be shipped in carload lots by rail.
2. (b)If the nature of the supplies or safety, environmental, or transportability factors require special methods for securing the supplies on the carrier's equipment, or if only a special mode of transportation or type vehicle is appropriate, the contracting officer shall include in solicitations detailed specifications that have been coordinated with the transportation office.