Railway signal

Railway signals ( signal from Latin signum 'sign' ), optical, acoustical or electronic signals that transmit information in the form of signal aspects in the operation of the railway. They are used to secure train and shunting movements and the acceleration of the ground- operational course of operations.

In a narrower sense are meant the standing along a railway line route signals that convey the leader of railway vehicles information and orders or for the track. They are given by the Dispatcher or guards as an operator of a switchboard. Important information communicated with signals include, among others, may be driven whether and at what speed.


In the early days of railroad history, often as wrong only one or two trains on a track, very simple methods have been used for communication. The communication was performed using whistles, waving, swinging of flags or lanterns.

With an increasing number of trains, this was impractical and a time interval it was first introduced, after a train was allowed to follow another at a stretch. A distinction was made also by train type and speed, so that a passenger was allowed to follow a freight train only by a large margin, while he had to keep only a small distance by an express train. Despite different speeds thus always remained a sufficient distance between two consecutive trains and normally not a train colliding with another. However, this system entailed risks when a train remained on the track and the following this is not recognized in time.

Then, the space distance was introduced, which holds a free stretch each train and no one else may enter until the previous has left him. These distances were first realized by consuming marshals agreed on view with flags and lanterns. More on this later attached to masts discs or baskets were used, which were more visible and thus enlarged the block distance and the number of marshals declined. This process has been greatly simplified by the 1840 introduced railway telegraph, could be given to the electrical signals over long distances along railroad tracks.

With a wide variety of railway companies, a variety of signal posts and poles with movable elements that could be operated from the signal box wire coatings, electrically or otherwise developed. These mechanical semaphore signals provide a signal aspect by moving elements - usually panels or wings - represents the now increasingly common design is the light signal, wherein the signal lamps represent the signal terms by their color and arrangement. This resulted from the addition of lamps that need the semaphore signals for the night. Many signal jobs but still given by hand with the aid of signal flags and with light characters, so for example when maneuvering or to grant the Abfahrauftrages for a train.

Classification of signals

Signal term

Railway signals have been developed mainly for the transmission of the following terms: The respective signal images defines the railway signal order

  • Driving license
  • Speed
  • Direction ( track )
  • Additional company information
  • Vehicle- dependent additional information
  • Trackside additional information

Protection objectives of railway signals

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

Otherwise, include the following protection goals act ...

... to the driving position:

  • Change in velocity
  • Specific operating instructions

In maintenance ... Position:

  • End of the license
  • Protection of other routes
  • Protection from crossing and moving elements (eg lift bridges, military chamber goals)
  • Emergency in the event of an incident
  • Specific operating instructions

... in case of failure:

  • Operating instructions for further process ( eg driving to view)
  • Specific operating instructions

Signaling principle

A license may be a tractor alone are indicated (meaning with maximum line speed ), or with additional information about infrastructure ( with code letters for selection among alternative travel options ) or with the permissible speed:

  • Driving signaling ( signaling " stop" and " run"; signal is available at the start of train journeys )
  • Driving with implicit signaling Wegsignalisierung (originally British philosophy; signal terms straight, left or right branching )
  • Driving with implicit signaling speed signaling ( originally German philosophy; signal aspects ahead or abzweigund unpaged )
  • Driving signaling with combined distance and speed signaling ( North American, Eastern European and philosophy of modern signaling systems )

For a signaling of the infrastructure or the speed change may be markers (eg direction indicators, the start of a speed reduction ) without major signals stand alone ..

Signaling purpose

Railway signals serve different purposes, which are presented below:

Signaling the validity of signals

  • Invalid signals are mostly with the help of a white cross - for example, at the newly built, not yet valid signal - in.
  • If a signal is at a site different from the control, it transmits a mapping table or another additional sign.

Signaling of the license and of the infrastructure

  • Signaling the license
  • Signaling the direction of the travel

Signaling the maximum

  • Signaling permissible limits depending on the track alignment on the open road
  • Signaling permissible limits depending on the driveway for several driving opportunities, for example in the station
  • Signaling permissible speed limits for trains with specified brake systems
  • Signaling permissible maximum speed for tilting trains
  • Signaling permissible limits depending on other criteria (for example nachgeschoben trains)

Signaling of rail operations

  • Signaling to accelerate or slow down the movement of trains
  • Signaling for direction change
  • Signaling of driving on command from driving on view of driving in the cable operation of driving with tension rods, of driving in the interval and of other methods to secure the movement of trains
  • Signaling shunting
  • Signaling of areas for special railway operational requirements (for example nachgeschobene trains)
  • Signaling to contact the driver with the Dispatcher

Signaling in case of danger

  • Signaling a warning in case of danger
  • Signaling of areas for emergency brake
  • Signaling method to the case of signal interference

Signaling systems for securing the movement of trains and other rides

  • Signaling properties to the signal system
  • Signaling properties of the train control system to
  • Signaling of train detection sections

Special features of the railway infrastructure

  • Signaling to ride on certain tracks ( for example, when driving on the opposite track )
  • Signaling completion of a track
  • Signaling the gauge
  • Signaling of rack sections
  • Signaling of the locations, the position and the operation of movable driving elements (for example, railway points, derailers )
  • Signaling the location, the position and operation of the backup of level crossings
  • Signaling the pitch
  • Signaling the chainage
  • Signaling of holdings established locations
  • Signaling to the train dispatching
  • Signaling the loading gauge
  • Signaling the clearance gauge
  • Signaling to properties of the train radio
  • Signaling other properties of the railway infrastructure

Signaling for power supply ( traction )

  • Signaling by filling sites for steam locomotives and diesel locomotives
  • Signaling of evacuation sites for steam locomotives
  • Signaling for feeding sites for Akkumulatortriebfahrzeuge
  • Signaling of the traction power system
  • Signaling portions of the traction power system
  • Signaling the end of the overhead line or conductor rail

Signaling for certain characteristics of the traction unit

  • Signaling of selected information for certain rail cars (for example, for snow plows )
  • Signaling of selected information for specific train types (for example, for tilting trains )
  • Signaling the brake tests

Rail vehicle -side signaling

  • Signaling the Zugspitze and the rear of a train
  • Signaling of trains with certain characteristics

Grouping of signals

For visual representation of the signal aspect serve different groups of signals, which are grouped according to their operational function:

  • Main signal
  • Vorsignal
  • More section signal
  • Retry signal
  • Shunting
  • Group signal for multiple tracks (for example Gruppenausfahrsignal )
  • Special signals for the announcement and presentation of other information
  • Pole signs at signals to process in case of failure of these signals
  • On-board signals ( train signals )
  • Other signals

Signal positions

Depending on the number of displayed information and the option to not show signal terms, signals can occupy one or more positions:

  • Not switchable
  • Switchable
  • Freely programmable

Transmission range

Signals can not only be continuously transferred to the trains at individual sites, but also in sections or.

  • Punctual
  • Linearly
  • Radio- shaped

The area of ​​train control typically meets at least the possibility of the transmission range of the corresponding signaling for backup of schedules.


The signals may be transmitted in various ways:

  • Orally
  • In writing
  • Flags and objects (eg balloons )
  • Form signal ( description of the shape signal philosophies with color schemes )
  • Light signal (description of the light signal philosophies with color schemes )
  • Acoustic signal (eg whistle or crackers )
  • Cab signaling with electromagnetic transmission ( beacons, electromagnets, permanent magnets, railway line cables, cable line cable, radio manager)
  • Other modes of transmission (for example, experiments with light transmission )

For lines and radio transmission signaling and train control shaped often use a common transmission medium.

Signal control

The control of the signals can be performed according to different criteria and are triggered in different ways:

  • Rule-based (for example, when driving with tie rods )
  • Process- based ( for example, after retracting the block ahead section )
  • Event-based (for example, by pressing the emergency stop subways )

Signal systems

In the different countries, sometimes very different at the railway undertakings signaling systems have evolved. The framework for this is because of its operational safety significance usually part of the national railway law.

  • Railway signals in Germany are laid down in the railway signal order ( ESO). Railway signals are illustrated and described in so-called signal books for their use in practice.
  • The Japanese railway signals were determined in Japanese ministerial decree on technical standards of the railway. The signal system was initially based on the British way signaling, but was later influences of the U.S. speed signaling.
  • The railway signals in Finland consist of stationary light signals that cooperate with the train control system ATC.
  • Railway signals in Switzerland are divided into signals for speeds up to 160 km / h and a special cab signaling ( CAB Signalling) at higher speeds.
  • Railway signals in Austria are set by the signal V2 provision of the ÖBB. Approved they were by the Federal Ministry of Transport.

Cab signaling

On high-speed lines, a direct electronic transmission of signals to the traction unit is in addition ( for example, in the ICE or Shinkansen ) is used, since conventional optical signal aspects by means of lamps or form characters can no longer be perceived safe by the driver because of the high speeds. In addition, as an onboard computer can give support and implement the signal orders, if necessary without the participation of the driver directly.

The necessary for the driver information is thus represented in the cab of the vehicle over various gauges.

The German Federal Railway Authority requires that a driver needs to see a signal lying in front of him at least five seconds before he derives it an action. ( At 160 km / h so it lays 225 m back ). At higher speeds, because of an ATP system is used, the signal transmits information to the vehicle, in Germany for example, the automatic train ( LZB ) is used. Across Europe, here are several different systems in use, which will in future be unified in the form of the European Train Control System through a radio-based electronic system.

Also on subway and light rail routes cab signaling system is used to control trains. These are related train control systems in use, some of which also allow driverless operation.

Signals for the train crew and train signals

In Germany is mandatory for locomotives, a steam whistle or similar device for generating acoustic signals whistle by the Railway Construction and Operation (EBO ).

  • Departure whistle: Short whistles / horns: still " train is leaving. " Today partially usual but loud signal book no longer valid
  • Holding whistle: Long Whistles / Horns: " train stops. " Was to inform the brakeman used when there were no air brakes and for understanding other locomotives. Today no longer valid, instead there are special audio signals for brakes tighten and loosen.
  • Respect twist: Two times long whistles / horns: "Caution. " Today a moderately long tone.

As train signal includes headlight and tail lamp:

  • The peak signal ( Zg 1) consists of three A- shaped arranged white lights on locomotives and driving coaches or two horizontal white lights on a pushed car. This signal applies to both day and night.
  • The tail lamps ( Zg 2) consists of one or two red- white or red- yellow signs as day-sign and two horizontal red lights or reflective panels of the day- night as characters. The night sign with red light may blink.