A Bo-Bo-Bo in UIC classification

UIC classification

The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...

 is a locomotive

Locomotive

A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

 with three independent two-axle bogies with all axle

Axle

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

s powered. In the AAR system

AAR wheel arrangement

The AAR wheel arrangement system is a method of classifying locomotive wheel arrangements that was developed by the Association of American Railroads. It is essentially a simplification of the European UIC classification, and it is widely used in North America to describe diesel and electric...

, this is simplified to B-B-B.

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.

The arrangement is extensively used on Italian

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 and Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese railways. Other examples include New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's DJ

NZR DJ class

The NZR DJ class locomotive is a class of diesel-electric locomotive used in New Zealand. The class were purchased from Mitsubishi Heavy Industries with a modernisation loan from the World Bank to replace steam locomotives in the South Island, where most of the class members worked most of their...

, EW

NZR EW class

The NZR EW class locomotive was a class of electric locomotive used in Wellington, New Zealand. The classification 'EW' was due to their being electric locomotives allocated to Wellington.- Introduction :...

 and EF

NZR EF class

The NZR EF class is a class of 22 25 kV AC electric locomotives that operate on the North Island Main Trunk between Palmerston North and Te Rapa in New Zealand...

 classes; the Eurotunnel Class 9

Eurotunnel Class 9

The Eurotunnel Class 9 or Class 9000 are a series of 6 axle high power Bo'Bo'Bo' single ended electric locomotives built by the Euroshuttle Locomotive Consortium of Brush Traction and ASEA Brown Boveri...

 locomotives, which were themselves derived from the New Zealand EF class; the Swiss SBB

SBB

This article is about the Polish band. For the Michigan band, see Small Brown BikeSBB is a Polish progressive rock band formed in 1971 in Siemianowice, Upper Silesia by multi-instrumentalist and vocalist Józef Skrzek...

 Re 6/6 (Re 620); and the South Korea

South Korea

The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

n Korail Class 8000. China imported 6K electric locomotive

Electric locomotive

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

 from Japan between 1986 and 1987. The Bo-Bo-Bo design was applied to SS7 series except SS7E.

This wheel arrangement requires either an articulated frame or significant side play on the center bogie. The Italian locomotives and New Zealand EW class are articulated, whereas the Eurotunnel and New Zealand EF and DJ class locomotives' central bogies have a lot of sideplay.