Bo-Bo-Bo

A Bo-Bo-Bo or Bo′Bo′Bo′ (UIC classification) is a locomotive with three independent two-axle bogies with all axles powered by separate traction motors.

The Bo-Bo-Bo configuration is often used to lower axle weight while keeping lateral forces low compared to a locomotive with two three-axle bogies, thus allowing the locomotive to use lightly laid track, in particular narrow-gauge railways.

[4][5] The State Rail Authority of New South Wales, Australia built the last of its 86 Class electric locomotives (8650) in the Bo-Bo-Bo arrangement (called locally a Tri-Bo), but this did not prove successful and it spent long periods out of traffic undergoing repair.

The first Italian six-axle electric locomotives, such as the E.626, used a Bo′BoBo′ layout, where the two centre axles were mounted on a rigid frame and only the outer pairs on bogies.

[citation needed] This arrangement has been used for electric locos with three monomotor bogies, such as the Italian FS Class E.632 of 1982.