A standard classification for electric and diesel locomotives equipped with two bogies, each having two driven axles. The B indicates two powered axles, and the o indicates each axle has its own independent traction motor. This configuration offers excellent adhesion and negotiates tight curves better than six-axle units, making it ideal for passenger service and light freight.
We need a Bo-Bo for the yard transfer because a six-axle unit will pick the switch on that tight industrial spur.
In North American diesel terminology, this is often written as B-B, though Bo-Bo is the strict UIC classification.
Also heard as
- B-B
Do not mix it up with
- Co-Co: Bo-Bo indicates four powered axles total (two per truck), while Co-Co indicates six powered axles (three per truck).
Related terms
Co-Co
A locomotive wheel arrangement with two six-wheel trucks, all axles powered.
Bogie
A wheeled chassis or framework attached under a rail vehicle to provide support, suspension, and guidance along the track.
Traction motor
A heavy-duty electric motor geared directly to the axle of a locomotive or transit car.