This is a fairly superficial introduction to German railway signalling, intended to illustrate how different countries have evolved different solutions to the same basic problem of moving trains safely around the network.
Each European country has its own national variant traditional signalling system. Broadly, they may be divided into two types:-
- Route signalling, as in the U.K., where the specific route set is indicated to the driver
- Speed signalling, as in Germany and most European countries, where the maximum safe train speed is indicated to the driver, but the particular route set is not indicated.
In Germany, early colour light signals are according to system 'HV' using red, yellow, green and white lamps. More modern installations use system 'KS' where the signal lamps are supplemented by speed indicators for both Main and Distant signals.
The Hauptsignal (Main signal) is a stop signal. To allow sufficient braking distance for a train to stop at an adverse signal, each Main signal is preceded by a Vorsignal (Distant signal). This is a warning signal which may be passed when showing a restrictive aspect. The sequence of Distant signal, Main signal suffices where main signals are at least 1300m apart, otherwise a Distant signal is provided on the same post as the previous Main signal and, where this does not provide sufficient braking distance, also on the Main signal previous to that.
The heading photograph shows two Hauptsignal (main signal) at the north end of Mannheim Hauptbahnhof. Signal P004 on the left controls northbound departures from platform 4 and signal P003 on the right applies to platform 3. I believe the 'double red' is to prohibit passing the signal for shunting purposes, as well as prohibiting departure. The green lamp is above the red signal lamps. Below are two diagonal white lights which, when lit, authorise shunting movements beyond the red signal. Below the shunting signal is the yellow lamp forming part of the main signal allowing the 'green over yellow' aspect. When 'green over yellow' is displayed, the speed indicator at the top of the post (backed by a triangular sighting board) indicates the authorised reduced speed, in km/h divided by ten. Mounted lower down the post is the Distant signal indicating the aspect of the next Main signal.
This Distant signal is provided halfway along platform 3 at Mannheim, serving as the warning for signal P003, visible in the background. To indicate that the signal is less than the braking distance from the Main signal, a white light is displayed to the left of the signal. There will have been a previous warning signal at the full braking distance. The distant signal has two 2-lamp clusters, each showing Yellow or Green. The picture shows the 'double yellow' warning. When the main signal is displaying a proceed indication, the Distant displays a 'double green'. Where necessary, the 'green over yellow' indication can be given, indicating that the following Main signal is showing proceed at less than the line speed.
This picture shows two more Main signals at the north end of Mannheim Hauptbahnhof. Signal P002 on the left controls northbound departures from platform 2 and is showing 'double red'. Again, there are green and yellow lamps, plus a shunting signal and a numeric speed indicator at the top of the post. The cluster of three lights forming an 'A' is the 'Substitution signal'. These white lights, when lit, authorise a train to pass a defective Main signal which cannot be cleared. Lower down the post is the Distant signal for the next main signal, with a white light to indicate that it is less than the full braking distance from the Main signal.
Signal P001 on the right applies to platform 1. The grouping of lamps is a little more compact and the Shunting signal has additional lamps. The Main signal is displaying 'green over yellow' for proceed at reduced speed, as indicated (in this case) by the '5' in the speed indicator at the top of the signal for 50km/h. Mounted lower down the post is the Distant signal showing 'double yellow' indicating that the next Main signal is displaying 'stop'.
An elevated shunting signal is shown on the extreme right, applying to southbound moves on platform 4. Note the climbing brackets attached to the post to allow access to the signal head and the reflective red and white identification panel attached to the post to make the signal more visible to an approaching train. Another shunting signal applying to northbound moves on platform 4 can be seen, just behind the approaching 'ICE' train. A similar signal is mounted on the platform canopy of platform 3.
A snatched (rather fuzzy) picture of a Main signal as we passed at speed. Main signal at the top of the post. Below this, a shunting signal displaying two white lights diagonally and below this the yellow main aspect (to permit 'green over yellow' to be displayed. The separate cluster of three (yellow) lights forming a 'V' is the Caution signal. When illuminated, it allows a failed main signal to be passed. Below this, is the familiar diagonal pair of 2-lamp clusters of a Distant signal. Lower down the post is the signal number plate and the red and white reflective identification panel. There is no access ladder but the construction of the post presumably facilitates climbing. There are, however two landings with handrails to assist the maintainer - one by the main signal cluster, one by the distant signal. Finally, notice the two signalling equipment cases at the foot of the post.
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Another Main signal, near Frankfurt. All the standard aspects are provided but, in addition to the Main signal speed indicator at the top of the post, there is a Distant speed indicator (displaying yellow numbers) beneath the Distant signal.
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A main signal mounted on a bracket, presumably to improve sighting, on the approach to Frankfurt. This is a 'KS' system 'Combination' signal. The three Main lamps (red, yellow, green) are arranged in an 'A' to serve as a combined Main and Distant signal. It displays 'single red', 'single yellow', 'single green' or (when the Distant Speed indicator is lit) 'flashing green'. There is a Speed indicator above the Main signal and a Distant Speed indicator below the signal. The red and white identification panel indicates a Main signal - the yellow triangular identification panel is used in the 'KS' system to indicate a Distant signal.
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A final example of a bracket signal, near Frankfurt Hauptbahnhof. This appears to be a 'KS' system Distant with yellow and green signal lamps and a Distant Speed indicator below.
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As can be seen, conveying speed information to drivers can result in quite complex trackside equipment so the trend is now towards 'Cab Signalling' where speed information is presented in the cab and there may be no fixed signals along the route. But that's another story.
The pictures in this article are taken from my collection on German Railways.
Information on railway signalling in Germany is taken from 'European Railway Signalling', published by A & C Black for the Institution of Railway Signal Engineers (ISBN 0-7136-4167-3).
