Railway signals in Germany are regulated by the Eisenbahn-Signalordnung (ESO, railway signalling rules). There are several signalling systems in use, including the traditional H/V (Hauptsignal/Vorsignal) system.
History
Reichsbahn Originally, the railway company of each German state had its own signalling system. After these companies were merged into the German Imperial Railway (Deutsche Reichsbahn), a common signalling system, the H/V system, was created based on two key types of signal. However, Bavaria was permitted to use its own designs of signal, with slightly different meanings, as part of the national scheme for many years thereafter.
Main signals (German: Hauptsignale) allowed the train to proceed or not. These signals were semaphores, whose arms had a circle on their right-hand end, and were painted white with red edges (occasionally the colours were reversed). There would be at least one arm, which meant "stop" when aligned horizontally and "proceed" when inclined upwards at 45 degrees. Up to two additional arms could be mounted below for different routes. They were inclined at 45 degrees upwards when a diverging route was to be taken, and aligned vertically when the main route was set. At night, a horizontal arm showed a red light, a diagonal arm showed a green and a vertical arm showed none.
Route signalling was changed circa 1930 to speed signalling. On a double armed-signal, one horizontal arm meant "stop" (aspect Hp 0), one inclined arm meant "proceed at line speed" (Hp 1) and two inclined arms meant "proceed at reduced speed" (Hp 2 – usually 40 km/h). Third arms were removed; in 1948, the green light of the lower arm was changed to yellow. This system is still in use today.
There were also distant signals (German: Vorsignale) to advise the driver as to what aspect the next main signal showed, so that they could slow or stop their train in time if necessary. Unlike in British practice, every main signal had its own distant; and each main signal-distant signal pair was worked from a single signal lever. German distant signals took the form of a yellow circular board with a black edge. If the board was visible, it meant that the main signal was at "danger". To indicate that the main signal was showing "clear", the board was flipped horizontally through 90 degrees so as to be practically invisible. If the main signal to which the distant applied was a double-armed one, then a yellow arm, bordered black, was mounted on the post below the disc. If the main signal showed "proceed at reduced speed", then as well as showing the disc, the arm was inclined at 45 degrees. At night, distant signals showed two lights, one diagonally left below the other. Reading downwards, green-green meant "expect clear" (Vr 1), yellow-yellow meant "expect stop" (Vr 0), and green-yellow meant "expect clear at reduced speed" (Vr 2).
The first colour-light signals had come into use, but were not widespread when the country was divided in 1949. These signals simply showed the night aspects of the semaphore signals, and as such are not considered as a separate signalling system. Only the S-Bahn systems in Berlin and Hamburg were equipped with newly designed colour-light signals at that time, of the Sv system.
Post WWII Two new companies were founded; the Deutsche Bundesbahn in West Germany and the Deutsche Reichsbahn in East Germany. The Reichsbahn kept the name of the old Deutsche Reichsbahn, to keep infrastructure and the right to operate trains in West Berlin. Both companies had their own regulations from then on and they continued separately until 1994 when the rail companies were reunified. Even today, the signalling systems of the two halves of the country differ, and although a new system has been created which will eventually become universal, the vast size of Germany's railway network means that different systems are likely to remain in use for many years to come. Even semaphore signals and mechanical signal boxes are still in use as of 2026, but with improved safety by using PZB and train radio.
West
The Deutsche Bundesbahn mainly kept the H/V signalling, with colour-lights directly replacing semaphore signals; nevertheless, the signals did change their design over the years. One very early change was the inclusion of shunting signals (Sh, Schutzsignale) into the main signal's head. This affected mainly exit signals. These signals show two red lights to disallow any train or shunting movements and a red-white-white combination to allow shunting movements only. Later the subsidiary signal aspects (Zs 1, Zs 7, Zs 8), which had their own head, were also merged into the main head. Therefore, several signals, whether main, (certain types of both) subsidiary or shunting, can be merged into a common rectangular head.
The signalling system didn't change much to allow Gleiswechselbetrieb (regular wrong line working - i.e. running on left-hand track instead of right-hand). Only a new aspect (Zs 6) was created to inform the driver if they were to be diverted onto the wrong line.
Several minor experiments with new signalling systems were made, but only one survived: the Augsburg - Donauwörth line, equipped with Sk-type signals. A few of these signals still exist, and the new common (West and East) Ks signalling system was developed from these.
East The Deutsche Reichsbahn in the former GDR adopted a new colour-light signalling system from the OSShD (an international organization of railways, mainly "Eastern" ones). In East Germany, the system got the abbreviation Hl and was installed on many lines. A few older H/V colour-light signals did exist in some places where they were installed before the war or in the first years after war.
Reunification Several signalling systems and two sets of railway regulations exist within reunified Germany. The regulations are being gradually merged to form a single set, a process still in progress. Most of the network will come under the control of centralized signal boxes; during this process complete lines generally change to the new common Ks signalling system. However, old-style signals are still installed on a few new lines for various reasons, usually if no surrounding lines have Ks-type signals. Even new semaphores are still occasionally installed, though now mainly as spares in semaphore-only areas. Currently no new signalling system is being developed; the current systems are perfectly adequate for today's operations. The next step will be a system without fixed signals, based on ETCS.
The different signal systems The signal systems H/V (in both semaphore and lights-only implementations), Hl and Ks look quite different in appearance and differ in several details, but the safety principles are very similar, so the PZB safety system (see below) is used for all of them. (Note: the systems Sk and Sv are not covered by this article yet.) Most instances of the additional signal types (like Zs, Ne) can be combined with all the signal systems, e.g.: Zs 3(v) (speed limitation) appears with H/V and Ks, but Hl uses its own speed display; Zs 1 and Zs 8 appear with all of them, but in different shape. Lines without these signal systems exist: high-speed lines may operate practically without visible signals (except for a fall-back) and PZB: they use Linienzugbeeinflussung (LZB) or European Train Control System (ETCS) secondary lines under Zugleitbetrieb may use simplified signalling down to a Ne 1/Ne 2 combination (the one shown in #Example 1), where movement authority is granted by phone/train radio communication
Historically, many signals were given (and can still be given) by hand, e.g. with a lamp or a staff, or the train drivers follow verbal or written orders. Optimization led to the installation of fixed signals, requiring less personnel and improving safety, and the use of telephones and train radio (today: GSM-R).
Punktförmige Zugbeeinflussung (PZB)
A safety system with functionality similar to PZB is mandatory for nearly every train and most railroad lines in Germany (exceptions comprise shunting, single train operation, operation with very low speed, and freight-only operations). LZB and ETCS lines may omit PZB. Segregated networks like the Berlin S-Bahn also often use different safety systems.
Normally, a main signal showing Hp 0 ('halt') is protected by an active 2000 Hz magnet of the PZB train safety system which triggers a train trip ("Zwangsbremsung"; literally forced braking) if the train passes the signal. This may be overridden by holding down the Befehlstaste ("Command" button in the cab) while passing the 2000 Hz inductor at no more than 40 km/h if a Zs 1, Zs 7, Zs 8 signal (see #Zusatzsignale) or written order instruct to do so. In addition, a signal showing Hp 0 may be preceded by an active 500 Hz PZB magnet to trigger the train's PZB computer to enforce speed limits, according to the train's braking capabilities, to ensure that the train can stop before the main signal. Starting a train against a 'halt' signal without a special order is considered a safety violation and covered by the PZB "restrictive supervision". Note: a "Lichtsperrsignal" (see #Schutzsignale) that is used for shunting can show Hp 0, but is only protected by PZB magnets if it can be the start or end of a train movement.
Distant aspects that announce 'halt' or 'proceed with low speed', like Vr 0, Vr 2, Ks 2, Hl 10 etc., are normally (except for repeaters) accompanied by an activated 1000 Hz magnet of the PZB train safety system. Passing it triggers hidden timers in the vehicle's part of the PZB system, which first checks that the driver acknowledges the distant signal, then it supervises the braking. If the acknowledgement does not occur in time or if, at any point, the system detects that the train's speed exceeds the limits of a certain braking profile, it engages full brakes and enforces a stop of the train.
Main signal/distant signal (H/V) system The most common system is the H/V (Hauptsignal/Vorsignal) system which consists of main signals and distant signals. Depending on the technology used in the signal box, these signals may be either semaphores or colour light signals. The colour lights show the same light patterns the semaphores show at night. The aspects shown here may be accompanied by Zs 2, Zs 2v, Zs 3, Zs 3v, Zs 6 (see section #Additional signals) or Lf signals (see section #Langsamfahrsignale) in order to show speed limits or the choice of track that follows. A main signal (with lights only) is marked by a Mastschild (board with a colour code) to protect in case of a signal lights failure. The location of a distant signal is marked by an Ne 2 (unless it is a repeater or it is at the location of a main signal) to prepare for the case where the signal lights fail.
Hp 0: Stop A main signal (Hauptsignal) shows Hp 0 by a horizontal semaphore arm, one red light or two horizontal red lights. The signal requires the driver to stop in front of it. (Originally, the aspect with two red lights was called Hp 00 and had a different meaning than a single red light with regards to shunting, see #Schutzsignale, but nowadays, the meaning is the same. )
Vr 0: Expect stop A distant signal (Vorsignal) shows Vr 0 by a yellow disc or two yellow lights (the right light is above the left light). This signal indicates that its respective main signal shows Hp 0. As the signal is placed at braking distance from the main signal, the driver needs to apply the brakes immediately to stop the train before reaching the main signal.
Hp 1: Proceed Aspect Hp 1, indicated by one raised semaphore arm or a single green light, allows the driver to proceed at the speed indicated in their schedule.
Vr 1: Expect proceed