One statement that the author made probably is incorrect on its face. The author stated that "It featured two layers of wooden planks, with an insulating layer of cork or sawdust in between. This made the car more resistant to weathering and wear and tear, and it was able to carry heavier loads." The double sheathed boxcar was a 40 ton car, whereas the single sheathed car was a 50 ton car.
Ken is right about this description of the USRA double-sheathed car; it most certainly did NOT have an insulating layer.
I would also disagree with the statement that the double-sheathed car was “more successful.” The USRA single-sheathed car opened the eyes of many railroad chief mechanical engineers, and the day of the double-sheathed box car was ending. By 1925, very few were being built, to the USRA design or any other design. OTOH, it is true that many railroads re-roofed their USRA single-sheathed cars, as the roof chosen turned out not to be the best design.
