A Bo-Bo-Bo or Bo′Bo′Bo′ (

UIC classification The UIC classification of locomotive axle arrangements, sometimes known as the German classification''The Railway Data File''. Leicester: Silverdale, 2000. p. 52. . or German system,Kalla-Bishop P.M. & Greggio, Luciano, ''Steam Locomotives'', Cre ...

) is a

locomotive A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...

with three independent two-axle

bogies A bogie ( ) (in some senses called a truck in North American English) is a chassis or framework that carries a wheelset, attached to a vehicle—a modular subassembly of wheels and axles. Bogies take various forms in various modes of transp ...

with all

axle An axle or axletree 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 the vehicle, with the wheels rotating around the axle. In the former case, bearing ...

s powered by separate

traction motor A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric vehicle, electric or hydrogen vehicles, elevators or electric multiple unit. Traction motors are used in electrically powered rail vehicles (ele ...

s. In the AAR system, 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 A narrow-gauge railway (narrow-gauge railroad in the US) is a railway with a track gauge narrower than standard . Most narrow-gauge railways are between and . Since narrow-gauge railways are usually built with tighter curves, smaller structur ...

Bo-Bo-Bo locomotives

The arrangement is extensively used on

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

and

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

ese railways. Other examples include

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

's DJ, EW and EF classes; the

Eurotunnel Class 9 The Eurotunnel Class 9 or Class 9000 are six-axle high-power Bo′Bo′Bo′ single-ended electric locomotives built by the ''Euroshuttle Locomotive Consortium'' (ESCL) of Brush Traction and ABB. The class was designed for and is used exclusive ...

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

Re 6/6 The Re 620, Re 6/6 in the old numbering scheme, are six-axle, electric locomotives of the SBB-CFF-FFS, which were acquired as a replacement for the Ae 6/6 for heavy services on the Gotthardbahn. They are the most modern of the so-called "Gotthar ...

(Re 620); the

Russia Railways Russian Railways (russian: link=no, ОАО «Российские железные дороги» (ОАО «РЖД»), OAO Rossiyskie zheleznye dorogi (OAO RZhD)) is a Russian fully state-owned vertically integrated railway company, both managi ...

VL65, EP1 (EP1M), EP10 and

EP20 EP, ep, or Ep may refer to: Arts and entertainment Music * Extended play, a recording that contains more than a single, but less than a full album * Electric piano * Entity Paradigm, a Pakistani rock band * ''EP'' (The 77s EP), 1999 * ''EP'' (B ...

; and the

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

Korail Class 8000 The Korail Class 8000 locomotive is a series of South Korean electric locomotives operated by Korail. This locomotive was introduced from 1972 to 1990, after electrification of several industrial lines. It was assigned both passenger and fre ...

. China imported 6K

electric locomotive An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or gas ...

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

State Rail Authority The State Rail Authority, a former statutory authority of the Government of New South Wales, operated and maintained railways in the Australian state of New South Wales from July 1980 until December 2003. History The ''Transport Authorities Ac ...

of NSW 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 In structural engineering, a rigid frame is the load-resisting skeleton constructed with straight or curved members interconnected by mostly rigid connections, which resist movements induced at the joints of members. Its members can take bending mom ...

and only the outer pairs on bogies. This wheel arrangement requires either an articulated frame (becoming a Bo+Bo+Bo arrangement) or else 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.

B′B′B′ locomotives

A similar arrangement, but without separate traction motors for each axle, would be a B′B′B′ arrangement as UIC, indistinguishably B-B-B in AAR. This arrangement has been used for electric locos with three

monomotor bogie A monomotor bogie (french: bogie monomoteur) is a form of traction bogie (railway), bogie used for an electric locomotive or diesel-electric locomotive. It is distinguished by having a single traction motor on each bogie. Development The first el ...

s, such as the Italian

FS Class E.632 The FS E.632 and E.633 are two classes of Italian railways electric locomotives. They were introduced in the course of the 1980s. The locomotives are nicknamed ''Tigre'' ("tiger"). History The E.632/E.633 were the first Italian locomotives to ...

of 1982.

Bo′Bo′Bo′+Bo′Bo′Bo′ locomotives

These are a pair of Bo′Bo′Bo′ locomotives semi-permanently coupled as a single unit. They are each constructed with a single cab, giving a cab at each end. This layout includes Russian freight electric locomotives

VL15 The VL15 (Russian language, Russian: ВЛ15) is a Soviet Union, Soviet built electric mainline freight locomotive manufactured at the Tbilisi Electric Locomotive Works. The power supply was 3 kV Direct Current, and the axle arrangement Bo-Bo-Bo+Bo- ...

VL85 The VL85 (russian: ВЛ85) is a Soviet (and later Russian) built electric mainline freight locomotive manufactured at the Novocherkassk Electric Locomotive Plant (NEVZ) and designed under the management of V.Ya.Sverdlov (ru:В.Я.Свердлов ...

, VL86f and the experimental gas turbine electric locomotive GT1h-001, which was converted from an electric locomotive VL15.

Bo-Bo-Bo locomotives

B′B′B′ locomotives

Bo′Bo′Bo′+Bo′Bo′Bo′ locomotives

See also