Polish railway signalling

Polish railway signalling system provides complex outlook of traffic situation, yet is quite easy to understand. Signals can be divided into following categories:

• near and distant displays — signals (semi-automatic, automatic)
• distant-only displays — warning shields
• auxiliary — semaphore repeaters
• shunting — maneuver shields

Most signals are electric. Mechanical signals are in decline.

Colour Light Signals

Semi-automatic signals

Semi-automatic is the most important type of signal on Polish railways. Its name reflects the fact that it switches to a red (stop) aspect automatically after a train has passed it but it must be switched back to clear by an explicit action from a signal box or dispatch centre. It is the typical signal in use at stations.

A semi-automatic signal can be recognized by its post which is painted with red and white strips. Dwarf versions have their boxes painted so.

A red (stop) aspect on a semi-automatic signal must not be passed.

As presented on this compact chart, semi-automatic signals can display both near and distant functions. Near signals either command a stop or impose a certain speed limit beginning at that signal. Distant signals tell the driver what to expect at the next signal, especially when braking is required.

Distant signal
Vmax	100 km/h	60 or 40 km/h	Stop	unspecified
Vmax	100 km/h	60 km/h	40 km/h	Stop
Near signal

All permitted aspects on semi-automatic signals:
	S1 stop
Proceed or speed reduction order:
	S2 clear, proceed at Vmax S3 reduce speed to 100 km/h S4 reduce speed to 60 or 40 km/h S5 stop at next signal
Speed limit 100 km/h:
	S6 speed limit 100; will be Vmax after next signal S7 speed limit 100; will be 100 after next signal S8 speed limit 100; will be 60 or 40 after next signal S9 speed limit 100; will be stop at next signal
Speed limit 60 km/h:
	S10a speed limit 60 km/h; will be Vmax after next signal S11a speed limit 60 km/h; will be 100 after next signal S12a speed limit 60 km/h; will be 60 or 40 after next signal S13a speed limit 60 km/h; will be stop at next signal
Speed limit 40 km/h:
	S10 speed limit 40 km/h; will be Vmax after next signal S11 speed limit 40 km/h; will be 100 after next signal S12 speed limit 40 km/h; will be 60 or 40 after next signal S13 speed limit 40 km/h; will be stop at next signal

Subsidiary Signal
			Sz, the subsidiary signal (Pol. sygnał zastępczy) is a signal issued in case of malfunction. The first picture presents a typical case where the dispatcher cannot change the signal from S1. The second picture presents a case where the signal is powered down. Third picture presents a special signal where only the Sz sign can be displayed. The train must stop and wait until Sz is issued.

Automatic signals

Automatic signals are used on lines equipped with automatic block signaling. Their colour language is the same as aspects S1-S5 of semi-automatic signals. The main difference regards the S1 (red) aspect - After stopping, it can be passed but the subsequent maximum speed is limited to 20 km/h.

Automatic signals have their posts painted white (without red strips) to be easily distinguished from semi-automatic signals.

Automatic signals:
2-state ABS:
				S2 proceed S1 stop, train ahead
3-state ABS:
				S2 proceed (>1 block free) S5 stop at next signal (1 block free) S1 stop, train ahead
4-state ABS:
				S2 proceed (>2 blocks free) S3 reduce speed to 100 km/h (2 blocks free) S5 stop at next signal (1 block free) S1 stop, train ahead
other:
				S1a is a special-case aspect, which forbids passing a signal displaying it, just like S1 on semi-automatic signals. It is used for safety reasons, for example, to forbid entering a tunnel during fire alarm. Other aspects are displayed normally, as in 3- or 4- state ABS. (Unit - no aspect displayed) — on a track with bidirectional ABS, only the signals for currently set direction of travel will be illuminated; signals for "the opposite direction" will not be lit. A driver who finds himself approaching an unlit signal must stop the train and alert the dispatcher.

Warning shields

Warning shield sign

Warning shield (Pol. tarcza ostrzegawcza) is distant-only signal display. It is used on lines not equipped with ABS. Placed in the braking distance to allow the driver to stop before the signal ahead. Their colour language is the same as signal aspects S2-S5, making them technically a signal which is just incapable of displaying a S1 (stop) aspect.

Their posts are painted grey and equipped with the warning shield sign.

Warning shields:
	Os1 there will be stop at the (next) signal precedes S1, Sz
	Os2 there will be proceed with Vmax at the (next) signal precedes a signal with no speed restriction on its near signal: S2, S3, S4, S5
	Os3 there will be speed reduction to 100 km/h at the signal precedes a signal with a speed restriction of 100 km/h on its near signal: S6, S7, S8, S9
	Os4 there will be speed reduction to 40 or 60 km/h at the signal precedes a signal with speed restriction of either 40 or 60 km/h on its near signal: S10a, S11a, S12a, S13a (60 km/h); S10, S11, S12, S13 (40 km/h)

Repeater signals

When a signal aspect is not visible from the proper distance (because of track curves for instance), a repeater signal is installed to aid drivers. Up to three repeaters may be installed if needed. A repeater signal is not a substitute for a warning shield.

Their posts are painted grey and equipped with plates with Roman numerals: III, II, I where the "I" stands closest to the main signal. Their colour language is identical to warning shields, except the fact they also have a continuously glowing white light, which informs that this is not a main signal but a repeater.

Repeater signal:
	Sp1 there will be S1 (stop) at the signal
	Sp2 there will be proceed with Vmax at the signal
	Sp3 there will be speed reduction to 100 km/h at the signal
	Sp4 there will be speed reduction to 40 or 60 km/h at the signal

The following table presents as an example, a station-entry signal designated "B" displaying the aspect S13 (speed limit 40 km/h, stop at the next signal) preceded with warning shield and three repeaters:

warning shield		3rd repeater	2nd repeater	1st repeater	the main signal
ToB		3SpB	2SpB	1SpB	B
braking distance
		visibility distance

Level crossing warning shields

Level crossing warning shield is placed in a braking distance before an automatic level crossing. The signal tells the driver whether automobile drivers are warned about an approching train (blinking red lights, barriers). Normally, level crossing warning shields display no signal (i.e. are unlit). They light up in the front of an approaching train which is the first clue that the system is working correctly.

Level crossing warning shield signals are unrelated to other signals, therefore in case of Osp1 signal a train must proceed at 20 km/h regardless the higher speed allowed by last signal.

Their posts are painted black and white strips.

Level crossing warning shields
	Osp1 Automatic level crossing is not working properly. The front of the train must pass the crossing with its speed limited to 20 km/h and be prepared for an immediate stop.
	Osp2 Automatic level crossing operating properly. Proceed at normal speed.

Manoeuver shields - Shunting Signals

Manoeuver shield (Pol. tarcza manewrowa) is shunting signal, used exclusively at stations. A consist shunting on such signals must not leave the station. Manoeuver shields are either stand-alone or incorporated into semi-automatic signals, which bear letter "m" on such occasions.

Stand-alone manoeuver shields have their posts painted gray.

Manoeuver shields:
		Ms1 shunting forbidden S1 stop and shunting forbidden
		Ms2 shunting allowed

Mechanical signals

Mechanical semaphore (day & night)
Sr1 stop	Sr2 clear	Sr3 clear slowly (40 km/h)
Mechanical warning shield
On/Od1/Ot1 expect stop	Od2/Ot2 expect clear	Ot3 expect clear slowly
Mechanical maneuver shield
M1 shunting forbidden	M2 shunting allowed