Railway signal

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Railway signal with steam locomotive
Form pre- and main signals of a train station of the DB
Main light signal of the DB

Railway signals ( signal from the Latin signum 'sign') are optical , acoustic or electronic signals that convey information in the form of signal terms when the railway is in operation . They are used to secure train and shunting trips and to accelerate operations.

In a narrower sense, it means the route signals standing along a railway line, which convey information and orders about or for the route to the driver of railway vehicles . They are given by the dispatcher or attendant as the operator of a signal box . Important information that is transmitted with signals is, among other things, whether and at what speed it is allowed to drive.


In the early days of railroad history , when often only one or two trains ran on a route, very simple methods of communication were used. Communication took place by means of whistling, waving, waving flags or lanterns. The Liverpool and Manchester Railway was the first to introduce signals in 1830, which were given by flags : white for “stop”, red for “be careful, drive slowly” and purple for “free travel”. Other railways in Great Britain and the US followed suit in the early 1840s. The meaning of the colors used varied depending on the railway company and time. So green could also mean “stop”.

As the number of trains increased, this became impractical, and initially a time interval was introduced after which one train was allowed to follow another on a route. A distinction was also made according to type of train and speed, so that a passenger train was only allowed to follow a freight train at a great distance, while after an express train it only had to keep a short distance. Despite different speeds, there was always a sufficient distance between two successive trains, and normally no train could run into another. However, this safety system was dangerous if a train got stuck on the line and the following train was not informed in good time.

As a result, the spatial distance was introduced, which keeps a section of the route free for each train, into which no other may enter until the previous one has left it. These distances were initially realized by elaborate marshals who communicated on sight with flags and lanterns. Later, discs or baskets attached to masts were used, which were visible from a further distance and thus increased the distance between the blocks and reduced the number of marshals. This procedure was considerably simplified by the railway telegraph , introduced in 1840 , with which electrical signals could be sent over long distances along railway lines.

The various railway companies developed a large number of signal boards and masts with movable elements that were moved by the signal box in accordance with the state of the art at the time of their introduction via wire cables, electromechanically or in some other way. These mechanical shape signals represent a signal aspect through moving elements - mostly panels or wings. The design that has subsequently become increasingly common is the light signal , in which the signal lamps represent the signal aspects through their color and arrangement. These emerged from the night signals of the form signals, which became necessary early on with the expansion of rail operations into the darkness. In the second half of the 19th century, it was common in Great Britain to indicate that driving was cleared by a white light. Despite the risk of confusion, it was only given up in favor of a green light at the end of the 19th century. The German railways followed the example of the leading railroad country at the time: Until 1907, the main and distant signals in Germany were "driving" or "awaiting journey" at night with a white light. At the Royal Bavarian State Railways , this was maintained well beyond this point in time, as they shied away from the cost of retrofitting. This then led, among other things, to the Nannhofen railway accident in 1917.

Many signaling orders are still given by hand with the aid of signal flags and with light signals, for example when shunting or for issuing the departure order for a train .

Classification of signals

Signal aspect

Railway signals are essentially designed to transmit the following information:

  • driving licence
  • speed
  • Direction (route)
  • additional operational information
  • vehicle-dependent additional information
  • Trackside additional information

The signal terms used and the signal aspects that represent the terms are defined in the valid signal book .

Protection goals of railway signals

In the absence of a protection goal, the signal is in the basic position, which can be set to drive or stop depending on the signal system.

Otherwise, the following protection goals, among others, will take effect ...

... in driving position:

  • Speed ​​change
  • special operational information

... in stop position:

  • End of driving license
  • Protection of other routes
  • Protection against level crossings and moving elements (e.g. lift bridges, weir chamber gates )
  • Emergency stop in the event of an incident
  • special operational information

... in the event of a fault:

  • operational information on further procedures (e.g. driving on sight)
  • special operational information

Signaling principle

The driving license can be signaled to a train unit alone (meaning with the maximum route speed) or with additional information about the route (with identification letters for selection under alternative driving options) or with the permitted speed:

  • Driver's license signaling (signaling of "stop" and "travel"; signal is at the start of train journeys )
  • Driving license signaling with implicit route signaling (originally British philosophy; signal terms straight ahead, branching off to the left or right)
  • Driving license signaling with implicit speed signaling (originally a Central European philosophy; signal terms straight ahead or branching off without a page)
  • Driving license signaling with combined route and speed signaling (North American, Eastern European and philosophy of modern signal systems)

For signaling the route or the change in speed, indicators (for example direction indicators, the beginning of a speed reduction) can stand alone without main signals.

Signaling purpose

Railway signals serve different purposes, which are shown below:

Signaling the validity of signals

A pre- and main signal (block signal 731) at the
Kaiserbrücke West junction near the Mainz Nord stop , which are marked as invalid with a white cross with a black border.
  • Invalid signals are usually marked with the help of a white cross - for example on a newly erected, not yet valid signal.
  • If a signal at a location deviates from the rule, it has an allocation board or another additional information sign.

Signaling of the driving license and the route

Signaling the maximum speed

  • Signaling of permissible maximum speeds depending on the alignment on the open route
  • Signaling of permissible maximum speeds depending on the route with several travel options, for example in the train station
  • Signaling of permissible maximum speeds for trains with certain braking systems
  • Signaling of permissible maximum speeds for tilting trains
  • Signaling of permissible maximum speeds depending on other criteria (e.g. trains being pushed behind)

Signaling of railway operations

Signaling in case of danger

Signaling of systems to secure train journeys and other journeys

Special characteristics of the railway infrastructure

Signaling for energy supply (traction)

Signaling for certain characteristics of the train unit

Signaling on the rail vehicle side

  • Signaling of the Zugspitze and the end of the train
  • Signaling of trains with certain characteristics

Grouping of signals

ÖBB light signals (exit signals K103 and K105 with pre-signals, Hadersdorf am Kamp)

Various groupings of signals, which are differentiated according to their operational function, are used to visually represent the signal aspect:

  • Main signal (can also be a multi-section signal)
  • Distant signal
  • Repeat signal
  • Shunting signal
  • Group signal for several tracks (for example group exit signal)
  • Special signals for announcing and displaying other information
  • Mast signs on signals for procedures in the event of a fault in these signals
  • on-board signals (train signals)
  • Additional signal
  • further signals

Signal positions

Depending on the amount of information to be displayed and the possibility of not showing signal aspects, signals can be classified as follows:

  • not adjustable (fixed signal, license plate)
  • adjustable in one of several positions
  • freely programmable (e.g. free text display)

Transmission range

Signals can not only be transmitted to the trains at individual locations, but also in sections or continuously. One can differentiate:

Transmission type

The signals can be transmitted in different ways:

  • orally
  • written
  • Flags and objects (e.g. balloons)
  • optically as a shape signal (usually via the position of signal arms and signal discs)
  • optically as a light signal (usually via the color and arrangement of light sources)
  • Acoustic signal (for example whistles or bang capsules)
  • Driver's cab signaling with electromagnetic transmission (balises, electromagnets, induction coils, permanent magnets, rail line conductors, cable line conductors, radio conductors)
  • other types of transmission (e.g. experiments with light transmission)

With line and radio transmission, signaling and train control often use a common transmission type.

Signal control

The signals can be controlled according to different criteria and triggered differently:

Signaling systems

In the various countries, the railway companies have developed, in some cases, very different signal systems. Due to its importance in terms of operational safety, the set of rules for this is usually part of national railway law.

Cab signaling

On high-speed routes, a direct electronic signal transmission to the locomotive is also used (for example in the ICE , TGV or Shinkansen ), since conventional optical signal terms using lamps or shapes can no longer be safely perceived by the driver due to the high speeds. In addition, such an on-board computer can provide support and, if necessary, implement the signal tasks directly without the involvement of the driver.

The information required for the driver is shown in the driver's cab of the vehicle using various display instruments.

The German Federal Railway Authority requires that a train driver must see a signal in front of him for at least five seconds before he can deduce an action from it. (At 160 km / h he covers about 220 m). At higher speeds, train control systems are used that transmit signal information to the vehicle. In Germany, for example, line train control (LZB) is used. Several different systems are in use across Europe, which are to be standardized in the form of the European Train Control System by a radio-based electronic system.

Cab signaling is also used on underground and light rail routes to control trains. Related train control systems are in use for this, some of which also enable driverless operation.

Signals for the railway staff

In most countries, whistles or similar devices for emitting acoustic signals are required for locomotives. In Germany, a steam whistle or a comparable device such as a macro microphone for generating the acoustic signals is prescribed by the Railway Building and Operating Regulations (EBO) for traction vehicles . When continuous brakes were not yet available on all trains , signals were given to the train crew to apply or release the car brakes. Today acoustic signals are used to issue train personnel signals and to communicate with local personnel.

Train signals

Train signals are headlights and tail signals. In Germany, the headlights for trains (Zg 1) consist of three A-shaped white lamps on locomotives and control cars or two horizontal white lamps on a pushed car. This signal is carried out both day and night. The German end-of-train signal (Zg 2) consists of one or two red-white or red-yellow panels and two horizontal red lamps ( vehicle lighting ) as day signals and two horizontal red lamps or reflective panels of day signals as night signals. The night sign with red light is allowed to blink.

See also


  • Michael Dostal (ed.): Signals of the German railways . GeraMond, Munich, 2nd edition 2002, ISBN 3-932785-14-2

Web links

Commons : Railway Signal  - Collection of images, videos and audio files
Wiktionary: Railway signal  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. EUROPE TEACHING MATERIAL: Basic knowledge of rail professions. Haan-Gruiten, 2001, page 28. ISBN 3-8085-7401-1
  2. ^ Simon Garfield: The Last Journey of William Huskisson . Faber and Faber, 2002. ISBN 0-571-21048-1 , p. 135.
  3. ^ Lionel Thomas Caswell Rolt : Red for Danger . Edition: London 1978. ISBN 0-330-25555-X , p. 126, for the Great Western Railway 1865; Announcement No. 514 ( Stopping the trains in time ), p. 420. In: Eisenbahndirektion Mainz (ed.): Collection of the published Official Gazettes 7 (1903). Mainz 1904. Official Gazette of September 5, 1903. No. 45.
  4. ^ Lionel Thomas Caswell Rolt : Red for Danger . Edition: London 1978. ISBN 0-330-25555-X , p. 120.
  5. Hans-Joachim Ritzau: From Siegelsdorf to Aitrang. The railway disaster as a symptom - a study of the history of traffic . Landsberg 1972, p. 105.
  6. EUROPE TEACHING MATERIAL: Basic knowledge of rail professions . Haan-Gruiten, 1st edition 2001, page 384 ff. ISBN 3-8085-7401-1
  7. Signal book (SB) DV 301 of the Deutsche Reichsbahn Gesellschaft ( Memento from September 7, 2014 in the Internet Archive ) numbers 161-164