On the UK rail network, multiple working is where two or more traction units (locomotives, diesel multiple-units or

electric multiple-unit An electric multiple unit or EMU is a multiple-unit train consisting of self-propelled carriages using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number ...

s) are coupled together in such a way that they are all under the control of one driver ( multiple-unit train control). If the front locomotive of a pair in multiple has failed the driver can still control the rear locomotive for as long as air and electricity supplies are available on the failed locomotive. In tandem is when more than one diesel or electric locomotive are hauling a single train and under the control of a driver on each locomotive.

Locomotives

In the early days of diesel locomotives in the 1960s, locomotives worked within their class (i.e. two locomotives of the same class could work together but not with other classes). Locomotives from different manufacturers had varying methods of controlling engines or braking systems. If a train required more than one locomotive, an additional driver was needed, at extra expense. Since then, locomotives have been built to work with other locomotives in the same code or system. Similar systems are assigned a ''coupling code'', which is normally indicated on the front of the locomotive. Early diesels were also fitted with communicating doors in the nose which allowed the secondman to access the train heating boiler of the rearmost locomotive. The doors actually saw little use and, as they frequently caused draughts in the cab, many of them were later welded shut.

Multiple units

First-generation

First-generation diesel multiple units had the additional problem of differing types of

transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission ** ...

. For instance, a Class 127 unit ( hydraulic transmission) could be required to work in multiple with a Class 112 unit ( mechanical transmission). For this reason, the drive selector on the Class 127 was fitted with positions marked "D, 3, 2, 1" to change the gears when working in formation with vehicles with mechanical transmission. First-generation DMU coupling codes:

Second-generation

Most second-generation units built by

British Rail British Railways (BR), which from 1965 traded as British Rail, was a state-owned company that operated most of the overground rail transport in Great Britain from 1948 to 1997. It was formed from the nationalisation of the Big Four (British ra ...

were designed to use the BSI multiple working system, including members of the 14x Pacer and 15x Sprinter families. Some post-privatisation trains such as the Class 168,

170 Year 170 ( CLXX) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Clarus and Cornelius (or, less frequently, year 923 ''Ab urbe condita ...

and 172s were fitted with BSI couplers enabling them to operate in multiple with older stock, while other incompatible systems emerged. Examples included Dellner-couplers fitted to Class 171, 220,

221 __NOTOC__ Year 221 ( CCXXI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Gratus and Vitellius (or, less frequently, year 974 ''Ab ...

222 __NOTOC__ Year 222 ( CCXXII) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. In the Roman Empire, it was known as the Year of the Consulship of Antoninus and Severus (or, less frequently, yea ...

, 350,

360 360 may refer to: * 360 (number) * 360 AD, a year * 360 BC, a year * 360 degrees, a circle Businesses and organizations * 360 Architecture, an American architectural design firm * Ngong Ping 360, a tourism project in Lantau Island, Hong Kong ...

, 375,

376 __NOTOC__ Year 376 ( CCCLXXVI) was a leap year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Valens and Augustus (or, less frequently, year 1129 ''Ab ...

, 377,

390 __NOTOC__ Year 390 ( CCCXC) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Augustus and Neoterius (or, less frequently, year 1143 ...

, 700 and 710s while Scharfenbergs were fitted to Class 175 and 180s.Class 180
Angel Trains Franchise changes and stock reallocation means that many

train operating companies A train operating company (TOC) is a business operating passenger trains on the railway system of Great Britain under the collective National Rail brand. TOCs have existed since the privatisation of the network under the Railways Act 1993. T ...

use fleets with a number of incompatible multiple working systems.

References and sources

References

Sources

* {{DEFAULTSORT:Multiple Working Rail transport operations Rail transport in the United Kingdom