Swedish railway signalling

The signalling system used on the standard-gauge railway network in Sweden is based on that of the traditional mechanical semaphore signals. Currently only colour-light signals are used, together with the Automatic Train Control system.

Main signals

The main signals (huvudsignaler) display the following aspects:

	Meaning	Comment
Stop	The signal must not be passed without permission from the traffic control. During shunting operations permission to pass a home signal displaying stop may be given with a radio or with a dwarf signal.
Proceed 80	Authorises the driver to pass the signal at 80 km/h or at a higher speed given by the ATC system.
Proceed 40, caution	Authorises the driver to pass the signal at 40 km/h (25 mph) or at a higher speed given by the ATC system. The next signal might be displaying stop if it is farther away than 450 metres, so the driver must approach the next signal cautiously and be prepared to stop short of it.
Proceed 80, expect stop	Authorises the driver to pass the signal at 80 km/h or at a higher speed given by the ATC system. The next signal is displaying stop, so the driver must decrease speed and approach the next signal prepared to stop short of it. Block signals on the Swedish ore line can show Proceed 80, expect stop with only one flashing green light (right image)	The next signal is between 800 metres (2,625 feet) and 3,000 metres (9,840 feet) away. If the distance to the next signal is more than 3,000 metres, a separate free-standing distant signal is used to govern the approach to that signal.
Proceed 80, expect proceed 80	Authorises the driver to pass the signal at 80 km/h or at a higher speed given by the ATC system. The next signal is displaying a proceed 80 aspect.
Proceed 80, expect proceed 40	Authorises the driver to pass the signal at 80 km/h or at a higher speed given by the ATC system. The next signal is displaying proceed 40, so the driver must decrease speed and approach the next signal prepared to pass it at a speed not exceeding 40 km/h (25 mph) or the speed shown on the ATC driver's display.
Proceed 40, short route	Authorises the driver to pass the signal at a maximum speed of 40 km/h (25 mph). The next signal is showing "stop" and is closer than 450 metres.	The next signal could also be a stop light at the end of the line, or an End Board (S-tavla).

The aspects may seem a little inverted, since a single green light means proceed 80, two green lights Proceed 40, caution and three green lights stands for Proceed 40, short route. In other words: more green means more cautiously. The speed limits apply to trains without Automatic Train Control (ATC) equipment. ATC signalling typically allow higher speeds.

Two light signalling (Malmö City Tunnel)

On some routes, for example the City Tunnel in Malmö, a simpler signal system is in use until ERTMS will be in full use.
This system uses two light signals with blue number signs (instead of yellow/white in normal signalling) and can show the following aspects:

Signal		Meaning
	Stop	The signal must not be passed without permission from the traffic control. During shunting operations permission to pass a home signal displaying stop may be given with a radio or with a dwarf signal.
	Clear 40 expect clear 40	Authorises the driver to pass the signal at 40 km/h (25 mph) or at a higher speed given by the ATC system. The next signal is displaying a proceed 40 aspect.
	Clear 40 caution	Authorises the driver to pass the signal at 40 km/h (25 mph) or at a higher speed given by the ATC system. The next signal is showing "stop" and is closer than 450 metres.

These signals should not be confused with normal main signals with two lights. They have yellow number signs, while the "Two light signal" have blue ones.

Distant signals

Distant signals (försignaler) are informational signals used to give an advance warning about the next home signal. Distant signal are typically located 800 to 1,200 meters (2,625 to 3,940 feet) in advance of the home signal in question.
Before the entry/home signal of a station, there always is a free standing distant signal, with the signature for the station on a board placed under the signal.
The aspects a free-standing distant signal can display are:

Signal		Meaning
	Expect stop	The next signal is displaying stop, so the driver must decrease speed and approach the next signal prepared to stop short of it.
	Expect Proceed 80	The next signal is displaying Proceed 80.
	Expect Proceed 40	The next signal is displaying proceed 40, so the driver must decrease speed and approach the next signal prepared to pass it at a speed not exceeding 40 km/h (25 mph) or the speed shown on the ATC driver's display..

The signal indication is the same as for the combined aspects in the main signals.

Dwarf signals

Dwarf signals (dvärgsignaler) are used as shunting signals and can show the following aspects:

Signal		Meaning	Comment
	Stop	The signal must not be passed without permission from the traffic control.
	Movement allowed	Shunting allowed. Points and derailers are in the right position. The track is free.
	Movement allowed Track not clear	Shunting allowed Points and derailers are in the right position. The track is not free, or caution is needed.
	Movement allowed Check points and clearance	Shunting allowed The driver must manually check the position of points and derailers, and the track clearance. Points and derailers are often manual or put in shunting mode.

There are also types of dwarf signals, called "Main Dwarf signals" (Huvuddvärgsignal) used as stand-ins for home signals in stations with lot of shunting or where there are a lot of switches that needs a signal.

Road crossing signals

Road crossing signals (Vägkorsningssignaler (V-signaler)) are used at road crossings. They tell the driver if the crossing is clear (lights flashing, bells ringing or, if available, gates are closed) They can show the following aspects

Signal		Meaning
	Stop before crossing (Crossing not clear)	The road crossing is not secured. The train must stop before the crossing if possible.
	Pass (Crossing clear)	The road crossing is secured.

The same aspects are also used at moveable bridges, but with another sign under the signal.

Distant road crossing signal

Some road crossing signals have a distant signal (Vägkorsningsförsignal (V-försignal)), placed at a distance (usually not breaking distance) from the road crossing signal.

Signal		Meaning
	Expect Stop before crossing (Crossing not clear)	The road crossing is not secured. The train must stop before the crossing if possible.
	Expect Pass (Crossing clear)	The road crossing is secured.

The distant road crossing signal is nicknamed "skull" (döskalle).

Fail safe

Because the aspects are in reverse with more green lights meaning slower the aspects are not fail safe, so lamp proving is needed to prevent lamp failure giving a faster aspect.

Single and Double Green signals work the other way with Norwegian railway signalling and it would be unsafe for drivers to cross the border, unless ATP were fitted.

Sources

Swedish signalling section of The Signal Page (TSP)
Signalfakta by Per Forsström (in Swedish) at the Wayback Machine (archived May 27, 2007)

Railway signalling

Block systems	Absolute block signalling Automatic block signaling Centralized traffic control Communications-based train control Direct traffic control European Train Control System Moving block Radio Electronic Token Block Token Track warrant Train order operation

Signalling control	Block post Integrated Electronic Control Centre Interlocking Lever frame Rail Operating Centre Solid State Interlocking Westlock Interlocking

Signals	Application of railway signals Cab signalling North American railroad signals Railway semaphore signal

Train detection	Axle counter Track circuit Track circuit interrupter Treadle

Train protection	ALSN ASFA Automatic train control Automatic train protection Automatic train stop Automatic Warning System Automatische treinbeïnvloeding Balise Catch points Chinese Train Control System Continuous Automatic Warning System Contrôle de vitesse par balises EBICAB IIATS Integra-Signum Interoperable Communications Based Signaling Crocodile Linienzugbeeinflussung Positive Train Control Pulse code cab signaling Punktförmige Zugbeeinflussung RS4 Codici Sistema Controllo Marcia Treno Système d'aide à la conduite, à l'exploitation et à la maintenance Slide fence Train Automatic Stopping Controller Train Protection & Warning System Train stop Transmission balise-locomotive Transmission Voie-Machine

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