Locomotive

Locomotive, power unit used to haul railroad trains. The earliest railroad locomotives, invented in England in the early 19th century, used steam engines, which remained popular until the mid-20th century. Although electric locomotives have been in service in the United States since 1895, the high capital cost of converting tracks to electric transmission has prevented their widespread adoption. Since the 1950s, most U.S. locomotives have been built with diesel engines. Elsewhere in the world, particularly in Europe, much greater use is made of electric traction, the locomotives usually collecting power from overhead cables via a pantograph. Although some gas-turbine locomotives are in service in the United States, this and other novel power sources have not made much headway.