At DBAG signals are also classified depending on their usage:
In Germany the different usages of signals are not identified by the signal's design, i.e. the usage and placement rather than the appearance define whether we have e.g. an exit or a block signal. In some other European countries this is different.
All signals are placed immediately to the right of the track they are governing. On double lines where wrong line operation occurs regularly, the signals for the wrong (i.e. left) line are placed to the left of the left line.
Where lack of space prohibits the regular placement of signals, they are either mounted on a gantry above the respective track or placed to the left of the track. In the latter case a Ne 4 Chequerboard Sign is placed to the right of the track, the Ne 4 may be omitted when the location of the signal is mentioned in the local rulebook.
Entrance signals protect entries to stations. They are usually placed 200 m before the first 'point of danger', which could be a point a crossing or the tail of a halting train. Other distances (min 50-max 400 m) apply when the last 2 km before the signal include a gradient. On branch lines the distances can be reduced down to 50% but not shorter than 50 m. An entrance signal is usually capable of showing Hp 2 (slow) additionally to Hp 1/Hp 0 (clear/stop).
Exit signals are placed at the end of each track. Especially in stations with curved tracks the exit signals must be placed in a line that crosses the tracks either perpendicularly or diagonally, so that the signals appear in the same order, regardless of where the viewpoint is. On branch lines the exit signals may be omitted when the exit speed does not exceed 60 km/h.
To maximise the usable track length in a station, the signals should be placed as far as possible to the point area. On converging tracks however, since the signals also protect the following point(s) and movements on the other tracks, there must be sufficient distance between the exit signal and adjacent points or other tracks.
On freight yards or freight tracks Group Exit Signals may be used. This is a single signal placed after the last point where all tracks it governs join. Additionally at the end of each individual track a high line-close signal (Sh 0/1) is placed to be able to show which track exactly is cleared with the group exit signal.
Please note that a clear exit signal does NOT permit a halting train to depart - this is accomplished by the departure order signal.
Intermediate signals are the main signals within station limits. Note that in Pre-WW II eras the expression Zwischensignal had a different meaning: It then meant what now is called a distant signal repeater. This form of Zwischensignal is still used in Austria's ÖBB and there is called Signalnachahmer.
A block signal dividing the open line into blocks.
A covering signal protects special points of danger on the open line that are not covered by block or other signals. This may be e.g. points crossings or drawbridges.
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