One of two experimental demonstrator Aerotrains, numbered 2 and 3, was built by GM with a new lightweight construction and low center of gravity concept and powered by 1,200 h.p. futuristic locomotives. Initially used in mainline service, the trains rode poorly at high speeds and had very high noise levels. Purchased by the Rock Island Railroad, they served in suburban Chicago passenger service until 1965. The locomotive and two cars were donated in 1966 by the Rock Island Railroad.