Co-Co locomotive

The equivalent UIC classification (Europe) for this arrangement is Co′Co′, or C-C for AAR (North America).

Co-Cos are most suited to freight work as the extra wheels give them good traction.

The first C-C design recorded was a narrow-gauge Hornsby opposed-piston Hornsby-Akroyd-engined locomotive of 1903 for the Chattenden and Upnor Railway.

This provides the same number of axles for traction, although with shorter bogie wheelbases and so gives a smoother ride.

Each 'Co' bogie has an additional non-powered axle in an integral pony truck to spread the load.

These were used in South Africa, for lighter loadings on the lightly laid 3 ft 6 in (1,067 mm) Cape gauge.