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Signalling in NSW

This is a brief (but hopefully still accurate!) overview of signalling as used in NSW. I am not safeworking expert, so if there are errors please let me know.

Double Colour Lights

Double light signals are used mainly in the area where suburban and inter-urban passenger trains are used. The top light indicates whether a train can proceed or not, whereas the second light indicates the state of the next signal down the line. Giving the driver an indication of the following signal allows closer and more efficient running of trains in the busy CityRail network.

Often only a subset of these signals are used. In much of Sydney you will only see STOP, CAUTION and CLEAR aspects.

These signals are divided into two types: controlled (also known as absolute) and automatic (a.k.a. permissive). Controlled signals are operated by signal boxes and allow for protection of junctions and such. Automatic signals are not directly controlled; their purpose is to maintain the separation of trains.

Automatic Signals

Automatic signals can be distinguished from controlled signals in that the lights are vertically offset from each other.

	Indication	Meaning		Indication	Meaning
	STOP	Stop.		MEDIUM	Proceed; the next signal displays at least a CAUTION or CAUTION TURNOUT indication.
	LOW SPEED	Proceed ready to stop at the next signal. Where train stops are provided, a maximum speed of 25km/h applies (only applicable at signals with a low-speed indicator).		PRELIMINARY MEDIUM	Proceed. The next signal displays at least a MEDIUM indication.
	CAUTION	Proceed; the next signal may be at stop.		CLEAR	Proceed.

Controlled Signals

Controlled signals are controlled from a signal box. They are typically used before facing junctions and other areas which need protection.

	Indication	Meaning		Indication	Meaning
	STOP	Stop.		MEDIUM TURNOUT	Proceed through the turnout. The next signal displays at least a CAUTION or CAUTION TURNOUT indication.
	LOW SPEED	Proceed ready to stop at the next signal. Where train stops are provided, a maximum speed of 25km/h applies (only applicable at signals with a low-speed indicator).		MEDIUM	Proceed; the next signal displays at least a CAUTION or CAUTION TURNOUT indication.
	CAUTION TURNOUT	Proceed at medium speed through the turnout; the next signal may be at stop.		PRELIMINARY MEDIUM	Proceed. The next signal displays at least a MEDIUM indication.
	CAUTION	Proceed; the next signal may be at stop.		CLEAR	Proceed.

Single Colour Lights

Single colour lights come in several varieties, but the following usage is typical.

	Indication	Meaning		Indication	Meaning
	STOP	Stop.		MEDIUM	Proceed; the next signal displays at least a CAUTION or CAUTION TURNOUT indication.
	CAUTION	Proceed; the next signal may be at stop.		CLEAR	Proceed.

Semaphore Signals

Lower Quadrant Signals

Home	Indication	Meaning	Home	Indication	Meaning
	STOP	Stop.		CAUTION	Proceed; the next signal will be at stop.
	CLEAR	Proceed.		CLEAR	Proceed.

Upper Quadrant Signals

Signalling Terminology

Home Signal

A signal which protects an interlocking area, for example a junction, crossing or yard.

Outer Home Signal

A signal which protect the region outside a home signal.

Distant Signal

A caution signal which warns of a following home signal.

Landmark Signal

Effectively a distant signal fixed at caution.

Starting Signal

The signal which controls the entry of a train into the next section.

Other Signals and Related Equipment

Guard's Indicator

This is a small black box usually mounted under the awning at a station, with the words "GUARDS INDICATOR" written above a white light. This light is illuminated when it is safe for the train to leave the station. It is provided for the train guard, so that he/she does not blow the whistle for the train to leave when it is not safe to do so.

Train Stop

Throughout the Sydney metropolitan network, you will notice a silver box with an arm attached to the side which can be raised or lowered. These are situated on the left hand side of the track, usually next to a signal. These are known as train stops. When a signal prevents a train from proceeding, the arm is raised. If a passenger train attempts to pass the location, the arm hits the trip valve on the front, which forces the brakes to come one.

You might also notice these spread out along the platform at City Circle stations. These are used in conjunction with low-speed signalling to allow trains to run closer than normal, while still preventing a collision.

Landmark Signal

A yellow triangular which serves as a fixed distant signal. It is used to indicate that a train should approach with caution. These are often seen on country branch lines at the approaches to significant locations.