A Bo-Bo (UK usage) or Bo′Bo′ (UIC notation) is a locomotive with two independent four-wheeled bogies with all axles powered by individual traction motors (cf B-B). Bo-Bos are mostly suited to express passenger or medium-sized locomotives.
Typical Bo-Bo locomotives include DB Class 120, FS Class E464 and SJ Class Rc.
In AAR notation a Bo-Bo is regarded as a B-B because the AAR system does not take traction motors into consideration, only powered axles.