This type of locomotive contains a massive diesel engine, main alternator, and traction motors, but lacks a crew cab and windshields. It is permanently or semi-permanently coupled to a standard locomotive equipped with a cab. Railroads use them to add raw horsepower to heavy trains without the expense of outfitting and maintaining redundant crew compartments.
Heard on the job
The dispatcher gave us a consist with two standard units and a B-unit sandwiched in the middle for the grade.
Insider tip
B-units are easily identified by their flat, boxy ends and lack of windows, earning them the nickname covered wagons in the early diesel era.
Also heard as
- booster unit
- cabless unit