Because of their low side walls, gondola cars are also suitable for the carriage of such high-density cargos as steel plates or coils, or of bulky items such as prefabricated sections of rail track.
[2] Those cars were not widely used at first, because they could only be unloaded by workers shoveling out the cargo by hand, a slow and labor-intensive process.
[2] After the American Civil War, advances in technology, especially the development of steel, allowed new and larger gondola designs.
New gondolas were built with steel sides and frames, although wood was retained for flooring since it was flexible and cheap to replace.
These gondolas are side-tipping, so they often are used to carry rock or dirt to add to an embankment, rather than dump crushed-rock ballast between the ties.