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Push–pull is a configuration forlocomotive-hauledtrains, allowing them to be driven from either end of the train, whether having a locomotive at each end or not.
A push–pull train has a locomotive at one end of the train, connected via some form of remote control, such asmultiple-unit train control, to a vehicle equipped with a control cab at the other end of the train. This second vehicle may be another locomotive, or an unpoweredcontrol car. This formation meant that the locomotive would not have torun-around at the end of a journey before returning.
The trains were also historically knows as "motor trains" or "railmotors", but the term "railmotor" is now used to refer to trains where the locomotive was integrated into a coach. In the UK and some other parts of Europe, the control car is referred to as adriving trailer (ordriving van trailer/DVT where there is no passenger accommodation); in the US and Canada, they are calledcab cars and in Australia, they are called driving trailers.
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Historically, push–pulltrains with steam power provided thedriver with basic controls at the cab end, including the regulator, brake andtrain whistle. The cab would also be provided with a bell or other signalling code system to communicate with thefireman, who remained on the locomotive to tend to the fire, in order to pass commands to adjust controls not available in the cab.
At low speeds, some push–pull trains are run entirely from the engine with the guard operating bell codes and brakes from the leading cab when the locomotive is pushing the train.
Manymountain railways also operate on similar principles in order to keep the locomotive lower down than the carriage to prevent any opportunity for a carriage to run away from a train down the gradient and also so that even if the locomotive ever ran away, it would not take the carriage with it.
Moderntrain control systems use sophisticated electronics to allow full remote control of locomotives. Nevertheless, push–pull operation still requires considerable design care to ensure that control system failure does not endanger passengers and also to ensure that in the event of aderailment, the pushing locomotive does not push a derailed train into an obstacle, worsening the accident. The 1984Polmont rail accident, in Scotland, occurred when a push–pull train struck a cow on the track.
When operating push–pull, the train can be driven from either the locomotive or the alternative cab. If the train is heading in the direction in which the locomotive end of the train is facing, this is considered 'pulling'. If the train is heading in the opposite direction, this is considered 'pushing' and themotorman orengine driver is located in the alternative cab. This configuration means that the locomotive never needs to be uncoupled from the train and ensures fast turnaround times at arailway stationterminus.
Alternatively, a push–pull train, especially a long one, may have a locomotive on each end so that there is always one locomotive pushing and one locomotive pulling. In this case, caution must be used to make sure that the two locomotives do not put too much stress on thecars from uneven locomotives. It is usual to arrange matters so that the trailing locomotive supplies less power, i.e. that the locomotive at the front does more pulling than the locomotive at the rear does pushing. Having an independent locomotive, as opposed to a power car at each end, is also known in the railway world as atop and tail. When this configuration is used in the US, only one locomotive (usually the front locomotive) is allowed to providehead end power (HEP: electricity supply forheating, air conditioning and lighting) to the train. The two-locomotive formation is used by theInterCity 125; its Australian equivalent, theXPT;Brightline;Amtrak'sAcela;SNCF'sTGV;Taiwan Railways Administration'sE1000 series; andNew Jersey Transit's longestNortheast Corridor Linemultilevel trains.
This form of operation has not necessarily been a function of train length; sometimes it was the most convenient way to set up push–pull operation in pre-HEP days without converting coaches to cab control operation. A prime example of this was theReading Company which converted its small fleet of streamstyled heavyweight medium-distance coaches for itsnon-electric commuter operation, with a pair ofEMD FP7 diesels bracketing a single five-car train, to supplant the Reading's fleet ofRDCs. This train normally operated a weekday peak-hour round trip betweenReading Terminal,Philadelphia andReading, Pennsylvania, from the late 1960s until 1981, with operation in the last five years byConrail under contract toSEPTA.[1]
A rare but possible configuration has a locomotive in the middle of the train with control cars at both ends, as was, for instance, used for a time on the Brussels–AmsterdamBenelux train when there were control cars but no three-voltage (3 kV DC, 1.5 kV DC, 25 kV 50 Hz) locomotives supporting theERTMS train control system in use on the BelgianHSL 4 and the DutchHSL-Zuid. TheClass 28 TRAXX locomotives were later upgraded, and the service went back to "normal" push–pull operation.
Historically, theGreat Western Railway ran Autotrains with two driving coaches sandwiching a steam locomotive.[citation needed]
In this configuration, locomotives hauling a train are located other than at the front or the back. It may includeremote control locomotives in the middle of a train. If operational considerations or economics require, trains can be made longer if intermediate locomotives are inserted in the train and are remotely controlled from the leading locomotive.
The first company to use the system was theGreat Western Railway which, in 1904, equipped carriages and0-6-0 locomotives as anautotrain to run on theBrentford Branch Line (betweenSouthall andBrentford) as an experimental substitute for steamrailcars. Control was by rodding and the mechanism allowed the driving compartment to be either one or two carriages-distant from the engine. With the engine in the middle of a formation, up to four carriages could be used. To reduce the surprise of a locomotive at the "wrong" end of its train, some were initially fitted with panelling painted in carriage livery.[2] The experiment was successful and the company's remaining railcars were gradually converted for autotrain use and purpose-built units constructed.
Other companies followed the lead in 1905: theNorth Eastern andLondon, Brighton & South Coast Railway using a compressed-air method of control and theMidland Railway, using a cable-and-pulley mechanism. TheGreat Central deployed the trains in 1906, using cable controls similar to that of the Midland. By the 1920s, most companies had them and they remained in use until they were replaced bydiesel multiple units (DMUs) in the 1950s.[2]
In 1967, theSouthern Region, already familiar with operating electric multiple units, applied the technique to its services fromLondon Waterloo toBournemouth, which were operated byelectro-diesel locomotives.[2][3]
In the early 1970s, theScottish Region used a system with aClass 27 locomotive at each end of a rake of coaches that had been retrofitted with the necessary 'Blue Star'multiple working cables to control the remote unit; but some problems of delay in actuation were experienced. They were replaced in 1979 by a system in which aDriving Brake Standard Open (DBSO), converted from aMark 2, could control theClass 47/7 locomotive via computerisedtime-division multiplex (TDM) signalling through the train lighting circuits. This had the added benefit that intermediate carriages needed no special equipment, and was found more satisfactory. Such trains became widely used on the intensive passenger service betweenEdinburgh Waverley andGlasgow Queen Street.[2][4] When the push–pull sets were replaced by multiple units, the DBSOs were transferred to operate on theGreat Eastern Main Line betweenLondon Liverpool Street andNorwich, where they were modified to work withClass 86 electric locomotives.
The original system of using the Blue Star multiple working was later revived afterprivatisation as a way of allowing locomotive-hauled stock to replace multiple units on certain routes, thus increasing capacity without the complications of having to run around or drag a dead locomotive at the rear. It was used byFirst North Western andWessex Trains withClass 31s, and byAbellio Greater Anglia,Arriva Trains Northern,Northern Rail andArriva Rail North withClass 37s all withMark 2 carriages.[5][6][7][8] The same system was also adopted byNetwork Rail for its track observation trains, although on many trains one locomotive has recently been replaced by a DBSO modified to work with Blue Star.[9]
In 1988, 52Mark 3 Driving Van Trailers were built byBritish Rail Engineering Limited to allow it to replace life expired electric locomotives on theWest Coast Main Line. These operated withMark 2 andMark 3 sets.[10]
As part of the electrification of theEast Coast Main Line, 31Mark 4 Driving Van Trailers were built in the late 1980s byMetro-Cammell to operate withMark 4s coaches at the south end of theInterCity 225 sets. Some of these passed toTransport for Wales Rail in 2021 to work on their Holyhead to CardiffPremier Service.
In the 2000s, some Mark 3s have been modified to operate withClass 67 locomotives withArriva Trains Wales,Chiltern Railways andWrexham & Shropshire.
In 2019, newMark 5 carriages, one of which has a cab, entered service withClass 68 locomotives forTransPennine Express, in a push–pull configuration.
Córas Iompair Éireann's first push–pull trains were conversions of their2600 Class DMUs (Park Royal body,AEC motors) running with the long withdrawn201 ClassMetropolitan-Vickers Bo-Bo diesels re-engined with EMD 567 prime movers; the cars were subsequently renumbered in the 6100 series (Driving van trailers), 6200 series (trailer with "blind" cab end) and 6300 series (double-gangway intermediate car). In push–pull formation, they operatedDublin Suburban Rail services from 1971 until the inauguration of theDART EMU service in July 1984. The remaining push–pull trains operated on Dublin-Maynooth commuter services until they were supplanted by Cravens, and later by the modern2600 Class DMUs.
Iarnród Éireann employs push–pull trains of two different kinds. The first of these were built in 1996. These areDe Dietrich Ferroviaire–builtEnterprise push–pull sets, jointly owned withNorthern Ireland Railways for operation on theDublin to Belfast route. These are powered by201 Class locomotives.
The other type of push–pull train used in Ireland is theMark 4 type (not to be confused with theBritish Rail Mark 4 type). These sets, delivered in 2005–2006, are used exclusively on the Dublin to Cork route, again operated by 201 Class locomotives.
Between 1980 and 2009, Iarnród Éireann operated push–pull sets based on theBritish Rail Mark 3 design, with a non-gangwayed driving cab fitted.[11]These were operated with 201 Class locomotives, although in the past121 Class locomotives were also used. The sets originally operated in theDublin outer-suburban area and on theLimerick toLimerick Junction shuttle, but were gradually moved to mainline InterCity routes out ofDublin Heuston after the introduction of railcar sets elsewhere. The entire Mark 3 fleet was withdrawn in September 2009 and scrapped in 2014.
In June 1958,SNCF commenced operating steam trains in push–pull formation out ofGare de l'Est.[12]
The first major application of push–pull operation using the modern single diesel configuration was on theChicago & Northwestern Railroad, announced in 1958.[13] In 1959, the C&NW received its first Control Cab equippedBilevel rail cars for commuter use. The extreme efficiency and success of these trains is why almost all of the commuter rail services in the United States and Canada utilize 100% push–pull operation on their locomotive-hauled trains.[citation needed] Examples include:Chicago (Metra);New York City (Metro-North, theLong Island Rail Road andNew Jersey Transit);Philadelphia (SEPTA); theWashington, DC andBaltimore area (MARC andVRE);Boston (MBTA);Dallas-Fort Worth metroplex (Trinity Railway Express);the Greater Miami area (Tri-Rail); theSan Francisco Bay Area (Caltrain andACE);Southern California (Metrolink andCoaster);Toronto (GO Transit);Montreal (AMT); and theWasatch Front in Utah (UTAFrontRunner). Most of these systems (except for SEPTA and Metro-North) continue to utilize some type ofbi-level passenger cars for push–pull service, either partially or exclusively.
Amtrak has a number of converted Metroliner EMUs in service as cab cars on the Keystone Corridor, where they operate in conjunction with ACS-64 electric locomotives. In addition, many regional services, such as the Michigan Services,Downeaster, andCascades, are operated withNon-Powered Control Units –EMD F40PH locomotives converted to use as a cab control and baggage car, earning itself the nickname 'cabbage cars'. Similarly, theCapitol Corridor,Gold Runner, andPacific Surfliner services in California are operated in push–pull configuration using purpose-built cab cars and diesel locomotives.
TheMuskingum Electric Railroad was a private, coal-hauling railway in centralOhio that ran for more than 20 years with two driverlessGeneral ElectricE50C electric locomotives that ran backwards from the coal-fired powerplant they served to the mine where their trains were loaded by affixing bogie trucks, a headlight, and a horn to the last freight car on each train.
In 1996,Israel Railways began running GEC–Alsthom push–pull coaches. Since then, it has also acquired push–pull coaches fromBombardier andSiemens. As of 2016, the bulk of Israel Railways' passenger operations use push–pull coaches. All of them have one locomotive at one end and a control car at the other end.
TheNew South Wales XPT long-distance passenger trains used byNSW TrainLink operate in a push–pull operation. In the pastV/Line operatedP class push–pulls on interurban services toBacchus Marsh andWyndham Vale until 2017.South Australian Railways'2000 class DMUs could be found with at least one motor car and one cab car in a push–pull configuration until their withdrawal in 2016.
In the first quarter of the 20th century up to 13motor trains ran onNZR.[14]
Until 2015, theAuckland suburban network run byTransdev used rebuiltBritish Rail Mark 2 carriages in either four, five or six car configurations. Three to five SA class carriages and an SD class driving carriage, fitted with a cab, were coupled to aDC class (4- and 5-car) orDFT/DFB class (6-car) locomotive, leased fromKiwiRail.
All SA and SD class cars were rebuilt byHillside Workshops. Auckland also operated formerQueensland RailSX carriages in push–pull mode with twoDBR class locomotives.
Following electrification of most of the Auckland suburban railway network, these diesel units have been replaced by a modern electrical fleet that consist of one or two sets of 3 car units (each of which have one carriage that can service passengers with disabilities).
