B-B and Bo-Bo are the Association of American Railroads (AAR) and British classifications of wheel arrangement for railway locomotives with four axles in two individual bogies. They are equivalent to the B′B′ and Bo′Bo′ classifications in the UIC system. The arrangement of two, two-axled, bogies is a common wheel arrangement for modern electric and diesel locomotives.

The Indian locomotive class WAG-12B is a class of 25 kV AC electric locomotives that was developed in 2017 by Alstom with technological collaboration with Indian Railways. The model name stands for wide gauge(W), Alternating Current (A), Goods traffic (G) locomotive-12 . They entered trial service in 2019. A total of 410 WAG-12B have been built at Electric Locomotive Factory, Madhepura, Bihar, India.