In the mid-1930s, the Chicago Great Western Railway and then the New Haven Railroad began "piggyback" service (transporting highway freight trailers on flatcars) limited to their own railroads. The Chicago Great Western Railway filed a US federal patent in 1938 on their method of securing each trailer to a flatcar using chains and turnbuckles. Other components included wheel chocks and ramps for loading and unloading the trailers from the flatcars. By 1953, the Chicago, Burlington and Quincy, the Chicago and Eastern Illinois, and the Southern Pacific railroads had joined the innovation. Most of the railcars used were surplus flatcars equipped with new decks. By 1955, an additional 25 railroads had begun some form of piggyback trailer service.