Push–pull train
Push–pull is a configuration for locomotive-hauled trains, usually having a locomotive on one end and a control car on another, connected via some form of remote control, such as multiple-unit train control.
This formation meant that the locomotive would not have to run-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 a driving trailer ; in the US and Canada, they are called cab cars and in Australia, they are called driving trailers.
Train formation
Locomotive at one end
Historically, push–pull trains with steam power provided the driver with basic controls at the cab end, including the regulator, brake and train whistle. The cab would also be provided with a bell or other signalling code system to communicate with the fireman, 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.
Many mountain 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.
Modern train 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 a derailment, the pushing locomotive does not push a derailed train into an obstacle, worsening the accident. The 1984 Polmont 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 the motorman or engine 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 a railway station terminus.
Locomotive in the middle
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–Amsterdam Benelux train when there were control cars but no three-voltage locomotives supporting the ERTMS train control system in use on the Belgian HSL 4 and the Dutch HSL-Zuid. The Class 28 TRAXX locomotives were later upgraded, and the service went back to "normal" push–pull operation.File:Buckfastleigh - 5542 between two auto trailers.JPG|thumb|250px|A preserved GWR autotrain, running with the locomotive sandwiched between two driving coaches on the South Devon Railway.
Historically, the Great Western Railway ran Autotrains with two driving coaches sandwiching a steam locomotive.
History
Great Britain
Steam
Great Western Railway
The first company to use the system was the Great Western Railway which, in 1904, equipped carriages and 0-6-0 locomotives as an autotrain to run on the Brentford Branch Line as an experimental substitute for steam railcars. 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. The experiment was successful and the company's remaining railcars were gradually converted for autotrain use and purpose-built units constructed.Other railways
Other companies followed the lead in 1905: the North Eastern and London, Brighton & South Coast Railway using a compressed-air method of control and the Midland Railway, using a cable-and-pulley mechanism. The Great 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 by diesel multiple units in the 1950s.Electric and diesel
In 1967, the Southern Region, already familiar with operating electric multiple units, applied the technique to its services from to, which were operated by electro-diesel locomotives.In the early 1970s, the Scottish Region used a system with a 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 a Driving Brake Standard Open, converted from a Mark 2, could control the locomotive via computerised time-division multiplex 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 between and. When the push–pull sets were replaced by multiple units, the DBSOs were transferred to operate on the Great Eastern Main Line between and, where they were modified to work with electric locomotives.
The original system of using the Blue Star multiple working was later revived after privatisation 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 by First North Western and Wessex Trains with, and by Abellio Greater Anglia, Arriva Trains Northern, Northern Rail and Arriva Rail North with all with Mark 2 carriages. The same system was also adopted by Network 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.
Driving Van Trailers (DVTs)
In 1988, 52 Mark 3 Driving Van Trailers were built by British Rail Engineering Limited to allow it to replace life expired electric locomotives on the West Coast Main Line. These operated with Mark 2 and Mark 3 sets.As part of the electrification of the East Coast Main Line, 31 Mark 4 Driving Van Trailers were built in the late 1980s by Metro-Cammell to operate with Mark 4s coaches at the south end of the InterCity 225 sets. Some of these passed to Transport for Wales Rail in 2021 to work on their Holyhead to Cardiff Premier Service.
In the 2000s, some Mark 3s have been modified to operate with locomotives with Arriva Trains Wales, Chiltern Railways and Wrexham & Shropshire.
In 2019, new Mark 5 carriages, one of which has a cab, entered service with locomotives for TransPennine Express, in a push–pull configuration.
Ireland
's first push–pull trains were conversions of their 2600 Class DMUs running with the long withdrawn 201 Class Metropolitan-Vickers Bo-Bo diesels re-engined with EMD 567 prime movers; the cars were subsequently renumbered in the 6100 series, 6200 series and 6300 series. In push–pull formation, they operated Dublin Suburban Rail services from 1971 until the inauguration of the DART 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 modern 2600 Class DMUs.Iarnród Éireann employs push–pull trains of two different kinds.
The first of these were built in 1996. These are De Dietrich Ferroviaire–built Enterprise push–pull sets, jointly owned with Northern Ireland Railways for operation on the Dublin to Belfast route. These are powered by 201 Class locomotives.
The other type of push–pull train used in Ireland is the 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 the British Rail Mark 3 design, with a non-gangwayed driving cab fitted.
These were operated with 201 Class locomotives, although in the past 121 Class locomotives were also used. The sets originally operated in the Dublin outer-suburban area and on the to shuttle, but were gradually moved to mainline InterCity routes out of after the introduction of railcar sets elsewhere. The entire Mark 3 fleet was withdrawn in September 2009 and scrapped in 2014.
France
In June 1958, SNCF commenced operating steam trains in push–pull formation out of Gare de l'Est.North America
The first major application of push–pull operation using the modern single diesel configuration was on the Chicago & Northwestern Railroad, announced in 1958. In 1959, the C&NW received its first Control Cab equipped Bilevel 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. Examples include: Chicago ; New York City ; Philadelphia ; the Washington, DC and Baltimore area ; Boston ; Dallas-Fort Worth metroplex ; the Greater Miami area ; the San Francisco Bay Area ; Southern California ; Toronto ; Montreal ; and the Wasatch Front in Utah. Most of these systems continue to utilize some type of bi-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, and Cascades, are operated with Non-Powered Control Units – EMD F40PH locomotives converted to use as a cab control and baggage car, earning itself the nickname 'cabbage cars'. Similarly, the Capitol Corridor, Gold Runner, and Pacific Surfliner services in California are operated in push–pull configuration using purpose-built cab cars and diesel locomotives.
The Muskingum Electric Railroad was a private, coal-hauling railway in central Ohio that ran for more than 20 years with two driverless General Electric E50C 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.