USRA standard

The USRA standard locomotives and railroad cars were designed by the United States Railroad Administration, the nationalized rail system of the United States during World War I.

1,870 steam locomotives and over 100,000 railroad cars were built to these designs during the USRA's tenure.

The light versions were designed with an axle load of 54,000 lb (24,500 kg) permitting usage on the vast majority of railroads, while the heavy versions were designed to a maximum axle load of 60,000 lb (27,200 kg) for lines with more heavily constructed track.

The Norfolk and Western Railway, in particular, continued building this type after the USRA period, developing and modernising it over time, as its Class Y.

In general, double sheathed boxcars are like girder bridges, so all the support needs to come from the frame.

While some engineers did not trust the steel bracing to support a single sheathed car and ordered fishbelly frames for strength, others valued the savings in weight and ordered cars with simpler frames like the USRA SS design.