Co-Bo

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Co-Bo or Co′Bo′ is a wheel arrangement in the UIC classification system for railway locomotives. It features two uncoupled bogies. The "Co" bogie has three driven axles and the "Bo" bogie has two.

The arrangement has been used to even out axle loading. The weight distribution of the locomotive depends on the power unit, the engine and generator. If these are not placed symmetrically, the weight distribution is also biased to one end. Placing three axles beneath the engine end and just two beneath the other, with the lighter ancillaries, gives more even loading per-axle.