Multiple working
{{About|train operations in Great Britain||Multiple-unit train control}}
{{Short description|Several locomotives running with a single driver}}
{{Use dmy dates|date=September 2017}}
{{Use British English|date=September 2017}}
File:Multiple working equipment on 40135.jpg locomotive]]
File:E6016 and 33102 at Cheddleton.jpg and a Class 33 locomotive being coupled for multiple working]]
On the rail network in Great Britain, multiple working is where two or more traction units (locomotives, diesel multiple units or electric multiple units) 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.{{Cquote|Many main-line diesel-electric and hydraulic locomotives are capable of running in multiples of up to three under the control of one driver|||British Railways Diesel Traction Manual for Enginemen|{{cite book
| title = British Railways Diesel Traction Manual for Enginemen
| publisher = British Transport Commission
| year = 1962
| page = 184
}}}}
"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.
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Multiple units
{{Main article|Multiple unit}}
=First-generation=
File:Wessex Trains DMU 150266 - 153xxx.jpg and Class 150 working in multiple]]
First-generation diesel multiple units had the additional problem of differing types of 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.{{cite web |url=https://railcar.co.uk/type/class-127/interior-description |title=Class 127 DMU Interiors |access-date=2023-08-12 |author=The Railcar Association}} However, because of damage to mechanical transmissions caused by improper gear selection on coupled hydraulic units, the Class 127 units had their coupling code changed from Blue Square to Red Triangle, which differed from Blue Square in name only and was unrelated to an earlier Red Triangle code used for the Derby Lightweight hydraulics.{{cite web |url=https://railcar.co.uk/type/class-127/description |title=Class 127 DMU Description |access-date=2023-08-12 |author=The Railcar Association}}
First-generation DMU coupling codes:
| class="wikitable" |
| Coupling code
! Class |
|---|
| ■ Blue Square
| Most units with mechanical transmission, Class 113, Class 127 (until 1969) |
| ◆ Yellow Diamond
| Derby Lightweight (mechanical transmission), Metro-Cammell Lightweight, Class 129 |
| ▲ Red Triangle (1st use)
| Derby Lightweight (hydraulic transmission) |
| ★ Orange Star |
| ● White Circle |
| style="white-space: nowrap;"|▲ Red Triangle (2nd use)
| Class 127 (from 1969) |
=Second-generation=
Most second-generation units built by British Rail 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 and 172s[https://www.angeltrains.co.uk/Products-Services/Regional-Passenger-Trains/11 Class 172] {{Webarchive|url=https://web.archive.org/web/20200613052319/https://www.angeltrains.co.uk/Products-Services/Regional-Passenger-Trains/11 |date=13 June 2020 }} Angel Trains 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, 222, 350, 360, 375, 376, 377, 390,[https://www.angeltrains.co.uk/Products-Services/High-Speed-Trains/30 Class 390] {{Webarchive|url=https://web.archive.org/web/20160304185716/https://www.angeltrains.co.uk/Products-Services/High-Speed-Trains/30 |date=4 March 2016 }} Angel Trains 700 and 710s while Scharfenbergs were fitted to Class 175[https://www.angeltrains.co.uk/Products-Services/Regional-Passenger-Trains/42 Class 175] {{Webarchive|url=https://web.archive.org/web/20160304190108/https://www.angeltrains.co.uk/Products-Services/Regional-Passenger-Trains/42 |date=4 March 2016 }} Angel Trains and 180s.[https://www.angeltrains.co.uk/Products-Services/High-Speed-Trains/29 Class 180] Angel Trains Franchise changes and stock reallocation means that many train operating companies use fleets with a number of incompatible multiple working systems.
See also
References and sources
=References=
{{Reflist}}
=Sources=
- {{cite book
| last = Williams | first = Alan
|author2=Percival, David
| title = British Railways Locomotives and Multiple Units including Preserved Locomotives 1977
| publisher = Ian Allan
|year = 1977
| location = Shepperton
| isbn = 0-7110-0751-9
}}
{{DEFAULTSORT:Multiple Working}}