A road slug is a stripped-down locomotive chassis equipped with traction motors but no diesel engine. It draws electrical power from a coupled mother unit to provide additional tractive effort without the fuel burn of a second prime mover. Unlike yard slugs geared for heavy pulling at a crawl, these units are ballasted and geared for mainline speeds.
Put that road slug in the consist behind the leader so we have enough dynamic braking for the hill.
Do not mix it up with
- Yard slug: A yard slug is ballasted and geared specifically for low-speed switching, while a road slug can safely operate at mainline freight speeds.
Related terms
Slug
A heavy, motor-equipped unit without an engine that draws power from a coupled locomotive.
Yard slug
A low-profile, unpowered locomotive chassis equipped with traction motors to provide extra pulling force in a switching yard.
Mother
A fully equipped diesel-electric locomotive that provides electrical power to a semi-permanently coupled slug.
Traction motor
A heavy-duty electric motor geared directly to the axle of a locomotive or transit car.