The Marmon-Herrington Company, Inc. is an American manufacturer of axles and transfer cases for trucks and other vehicles. Earlier, the company built military vehicles and some tanks during World War II, and until the late 1950s or early 1960s was a manufacturer of trucks and trolley buses. Marmon-Herrington had a partnership with Ford Motor Company, producing trucks and other commercial vehicles, such as buses. The company may be best known for its all-wheel-drive conversions to other truck maker's units, especially to Ford truck models. Founded in 1931, Marmon-Herrington was based in Indianapolis, Indiana, with a plant in Windsor, Ontario, and remained in Indianapolis until 1963. It is now based in Louisville, Kentucky.

A trolleybus is an electric bus that draws power from dual overhead wires using spring-loaded trolley poles. Two wires, and two trolley poles, are required to complete the electrical circuit. This differs from a tram or streetcar, which normally uses the track as the return path, needing only one wire and one pole. They are also distinct from other kinds of electric buses, which usually rely on batteries. Power is most commonly supplied as 600-volt direct current, but there are exceptions.