Co-Co is the wheel arrangement for diesel and electric locomotives with two six-wheeled bogies with all axles powered, with a separate traction motor per axle. The equivalent UIC classification (Europe) for this arrangement is Co′Co′, or C-C for AAR.
A New Zealand DFT class Co-Co diesel-electric locomotive
LMS 10000 of 1947
The 1903 Hornsby locomotive
DRG E 93 class 3,355 hp heavy-freight electric loco of 1933
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 added carrying axle of the JNR Class ED62 Bo-1-Bo
JNR ED76 Bo-2-Bo
Alstom KZ8A Bo′Bo′+Bo′Bo′
China Railways SS4 of 1985, showing the two unit construction