Push locomotive

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A sliding locomotive , pushing locomotive or print engine is an extra-operated locomotive at the end of a train . Train journeys with the use of push locomotives are referred to as pushing trains , push service or push operation . Snow clearing trips with pushed snow plows or non-powered snow blowers are not considered pushing service.


The SOB pushed the Voralpen-Express over its 50 ‰ steep ramps until 2013 when there was heavy traffic . At the end of the steep section, the BDe 4/4 push motor car separates from the Voralpen-Express after being uncoupled at the last stop.

Push locomotives are used in freight and passenger trains to increase the pulling force, especially on steep inclines, or to push a heavy train inside a station. Push-pull locomotives (or intermediate locomotives) are used when the trailer load exceeds the permitted drawbar load . In doing so, they take over part of the pulling force to move the mass of the wagon and prevent the train from separating . They are operated manually or from the train-carrying locomotive via a wired control line (e.g. UIC control line), sometimes remotely controlled by radio . On the descent, the electric brake of the push locomotive can contribute to the braking performance of the train without wear and keep the train stretched. Vehicles may be hitched behind a pushing motor vehicle. A pushing motor vehicle is usually to be coupled to the train, except when it leaves the train on the free route. A coupled pushing locomotive is connected to the continuous brake of the train.

Whether the push locomotive is coupled to the train depends on the route conditions. Coupling takes place when the pushing locomotive can stay on the train as far as a station, where a traffic or operational stop is required anyway and from where, ideally, a return service is available. This is the case, for example, on pass routes with ramps on both sides, such as the Tauern Railway . If the route is only inclined on one side in such a way that additional traction is required and if the trains are not supposed to stop after the incline, they are pushed in uncoupled. The push-pull locomotive leaves the train at the end of the uphill section and returns to the starting station.

The problem with uncoupled pushing is that if the driver of the pushing locomotive is inattentive, the contact between the train and the pushing locomotive is broken. Because of the increasing tensile load, this can overload the couplings and lead to train disconnection. Starting up again is also tricky; the impact when running up can lead to derailments, especially in tight bends. To avoid both, detachable couplings were developed for the driver's cab of the sliding locomotive. One example of this is the Keller coupling .

Tender steam locomotives, which are to push uncoupled and return to the station of departure, must provide visibility for the staff when traveling with the tender ahead and also have a sufficiently high permitted speed in this direction. If neither is given, then a turning facility, usually in the form of a turntable , is required at both end points of the push mode . For this reason, tank locomotives with the most symmetrical drive possible were used.

Advantages and disadvantages

Pushing locomotives are to be distinguished from:

  • Locomotive sandwiches running in multiple traction with one locomotive each at the front of the train and at the rear of the train
  • Pushed push-pull trains with control cars at the front of the train and remote-controlled locomotives at the rear of the train
  • Intermediate locomotives that are lined up between the wagons of a train and are not allowed to transmit any impact forces
  • Closing locomotives, which are given to a train to avoid empty runs and which are only allowed to develop enough tractive power to transport themselves
  • non-working locomotives, which are set as wagons in the wagon train in addition to the locomotive for transfer.

Setting down a push-pull locomotive takes less time than uncoupling a leader locomotive or even adding and disconnecting an intermediate locomotive. Instead of dissolving the slip path , setting the route for putting the leader locomotive away and then setting the route again for the train to continue, it is sufficient to uncouple the pushing locomotive. The train can continue driving immediately after a simplified brake test. The advantage of using push-pull locomotives is that the necessary additional tractive effort is only provided where it is necessary to move the train load. A locomotive that can move the train on its own on steep ramps is usually not used to capacity on the other sections of the route.

Disadvantages are the personnel costs for the additional train driver and the limited impact forces, especially when operating with a screw coupling, in order to prevent the pushed wagons from derailing in the narrow curves of mountain railways and in points. In contrast to the use of pre-tensioning or intermediate locomotives, pushing them in leads to strains and upsets in the train.

Push locomotives are often used to push part of the trailer load so that the permitted tow hook load is not exceeded.

Push service in individual countries


In Germany, the signal Ts 1 is set up on routes where trains are regularly pushed along with uncoupled push-pull locomotives. It signals to the driver of a pushing locomotive where he should stop pushing and get away from the train. Well-known locations are at the Gemmenich Tunnel on the Montzen route near Aachen, at the Rudersdorf Tunnel on the Dill route , in Blankenheim (Mansfeld-Südharz district) on the Halle – Hann railway line. Münden and in Steinbach am Wald on the Hochstadt-Marktzeuln – Probstzella railway line (as of 2014). The pushing service on the Spessart ramp was given up in 2017 after the new line went into operation. In addition, the Filstalbahn is pushed along the Geislinger Steige, i.e. between the Geislingen (Steige) station and the Amstetten (Württ) station .

In order not additionally restrict the route passing ability by returning on the left Streckengleis sliding locomotives were at the end of regularly used Nachschiebeabschnitten stations , many of Lokkehrbahnhöfe were called, created. Its central element is an extended track connection as a turning and waiting track between the main tracks. The pushing locomotive comes to a stop in the area of ​​the sweeping station and drives back to the turning and waiting track. This means that the uphill track is free for the next trip. On the waiting track, you can wait for a suitable gap in the timetable for the return journey without obstructing the rest of the traffic. The sliding locomotive turning function has also been integrated into conveniently located, existing train stations.


Illumination of the vehicles of a train with a coupled sliding locomotive in Switzerland
Illumination of the vehicles of a train with an uncoupled sliding locomotive

In Switzerland, non-remote-controlled locomotives are generally to be placed at the head of the train. Push service is only permitted on certain routes. In 1991, the BLS introduced pushing service for freight trains with a trailer load of 1,300 to 1,600 tons on the Lötschberg mountain line, based on the model of the Brenner line of the ÖBB in order to avoid the time-consuming and space-consuming intermediate service . In 1992 the SBB followed suit on the Gotthard and Monte Ceneri routes . Intermediate service is still required on both mountain railways for freight trains with a trailer load of 1,600 to 2,000 tons. Pushing service is also on the southern network of the Südostbahn (SOB) and with an uncoupled pushing locomotive on the Buchs SG – Rheinbrücke sections , from Lausanne Triage towards Renens and Bussigny , La Chaux-de-Fonds – Les Hauts-Geneveys and La Chaux-de-Fonds –Renan BE allowed. With the commissioning of the Lötschberg and especially the Gotthard base tunnel as well as the sandwich traction of the Voralpen-Express of the SOB, the labor-intensive pushing service fell sharply.

See also: Railway section in the radio remote control article

English speaking area

In the English-speaking world, remote-controlled intermediate and push locomotives are called Distributed Power Units (DPU). Manned push-pull locomotives are called helpers in the USA , and unmanned ones are called DPUs.

See also: Distributed Power Unit


cogwheel locomotive ČD class 715 in 1997 on the Tannwalder cog railway


Web links

References and comments

  1. ^ 1 May Bodensee-Express to Lindau, in railway nostalgia trips Bebra ( Memento from February 15, 2017 in the Internet Archive )
  2. The SBB operating regulations for lining up the locomotives treat a shuttle train ( push -pull train ) as a pulled train. In the English-speaking world, a distinction is made between distributed power mode with intermediate and sliding locomotives and shuttle trains in push-pull mode .
  3. Spessart-NBS before the start of operations . In: Eisenbahn-Revue International . No. 6 . Minirex, 2017, ISSN  1421-2811 , p. 305 .
  4. ^ Fritz Jost: Pushing service on the Lötschberg . In: Swiss Railway Review . No. 1 . Minirex, 1992, ISSN  1022-7113 , pp. 18 .
  5. ^ Heinrich Fäh: Pushing service on the Gotthard route . In: Swiss Railway Review . No. 5 . Minirex, 1992, ISSN  1022-7113 , pp. 212-213 .
  6. Implementation regulations FDV, local regulations for train journeys and shunting movements. (No longer available online.) SBB, BLS AG, SOB, December 9, 2012, formerly in the original ; accessed on July 1, 2017 .  ( Page no longer available , search in web archives )@1@ 2Template: Dead Link / www.sbb.ch