This heavy vehicle receives electrical power from a coupled mother locomotive, converting the mother's excess generating capacity into tractive effort at low speeds. It is built without a diesel engine or a cab, and its body is cut down low to the frame. This low profile gives the engineer in the mother unit a clear, unobstructed view over the top of the slug while shoving long cuts of cars during switching operations.
Couple the mother and the yard slug to that heavy drag of coal hoppers, we need the extra traction to pull them over the hump.
Do not mix it up with
- Road slug: A road slug retains its high hood and often a cab for main line service, whereas a yard slug is cut down low for visibility during switching.
Related terms
Slug
A heavy, motor-equipped unit without an engine that draws power from a coupled locomotive.
Mother
A fully equipped diesel-electric locomotive that provides electrical power to a semi-permanently coupled slug.
Hump yard
A classification yard where cars are pushed over a small hill and roll by gravity into sorting tracks.