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Main signals

Type codes for main signals

AM: Inter-block signals between stations.
U and SU: Station exit signals. U is the last exit signal before the station border. SUs, if any, come before it.
I and SI: Station entry signals, decribed in greater detail below.

PU signals can also show main signal aspects.

TU signals are described here for convenience.

Main signal aspects

Main signal or PU showing
RED or YELLOW/RED or TU showing YELLOW »Stop«
Station entry signals that have a yellow lantern always light it up when they show Stop. The TU showing yellow was only valid for departing (or through-going) trains.
Round signal
YELLOW/GREEN »Go slowly«
Clear to the next main signal, but along a route with a reduced maximal speed. Only shown by station entry signals.
Main signal or PU showing
GREEN »Go«
The track is free until the next main next signal, which may not be clear itself. This aspect does not necessarily mean that the next signal actually shows a Stop aspect; some signals never shows Go through. This applies both to older installations without block signalling between stations, and to brand new installations such as the coming Øresund link where the physical signals show only Stop or Go and it is left to ATC to discriminate between the clear aspects.
Main signal or PU showing
GREEN BLINK or GREEN/GREEN or TU showing GREEN »Go through«
The track is free until the next main signal, which itself shows at least Go. On stations, the track is clear all the way through the station, and the primary exit signal shows at least Go.

Station entry signals

There may be multiple entry signals in the entry of a station; the first one, with code I, officially marks the boundary of the station area. The secondary signals have code SI.

Station entry signals are visually distinguished by having a yellow lantern and thus being able to show the Go slowly aspect. In order to convey what the reduced speed is these signals are either equipped with a fixed speed sign or a speed code board showing patterns of white light. Speed code boards show the permitted speed whenever the signal displays a Go variation.

Some entry signals have branch indication The figure shows some sample aspects of such a signal. Their distants can be similarily branched.

Distant signals

Station entry signals from lines without automatic block signalling are preceded by distant signals. Distants have base plates whose bottom ends are semicircular and whose top ends are cut off recangularly. On a few very old block signalled lines, block signals as well as entry signals have distant signals, and the block signals do not indicate the indication of the next signal.

Distant aspects

Distant signal showing
YELLOW BLINK »Stop or Go slowly ahead«
Note that distant signals (or the advance signalling from main signals) do not discriminate between Stop and Go slowly aspects.

GREEN BLINK »Go ahead«

GREEN/GREEN BLINK »Go through ahead«

This page was last updated: May 30th 2001.

Henning Makholm <henning@makholm.net>

RED or YELLOW/RED or TU showing YELLOW	»Stop« Station entry signals that have a yellow lantern always light it up when they show Stop. The TU showing yellow was only valid for departing (or through-going) trains.
YELLOW/GREEN	»Go slowly« Clear to the next main signal, but along a route with a reduced maximal speed. Only shown by station entry signals.
GREEN	»Go« The track is free until the next main next signal, which may not be clear itself. This aspect does not necessarily mean that the next signal actually shows a Stop aspect; some signals never shows Go through. This applies both to older installations without block signalling between stations, and to brand new installations such as the coming Øresund link where the physical signals show only Stop or Go and it is left to ATC to discriminate between the clear aspects.
GREEN BLINK or GREEN/GREEN or TU showing GREEN	»Go through« The track is free until the next main signal, which itself shows at least Go. On stations, the track is clear all the way through the station, and the primary exit signal shows at least Go.

YELLOW BLINK	»Stop or Go slowly ahead« Note that distant signals (or the advance signalling from main signals) do not discriminate between Stop and Go slowly aspects.
GREEN BLINK	»Go ahead«
GREEN/GREEN BLINK	»Go through ahead«