Signals on the TTC

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The Toronto Transit Commission, or TTC, like most transit systems, uses a system of light-based signals to give instructions to their trains. They use block signals commonly, as well as interlocking signals. The TTC uses the NX/UR system of signalling, which is also used in New York on the New York City Subway, in Chicago on the 'L', and in Boston on the subway.

[edit] Block Signals

Block signals are the most commonly used signals on the TTC. They are used to keep trains properly spaced, and are controlled by the trains themselves, based on their distance relative to other trains. The following block signals are used by the TTC.

Two sets of signals are visible here, taken from the forward car of an eastbound train approaching Warden Station.

	Proceed
	Proceed With Caution
	Stop And Stay
	Entering Timed Block
	Timed Block, timer has not yet run out (red light flashes when timer is about to run out)

[edit] Interlocking Signals

A TTC interlocking signal

Interlocking Signals are used in interlockings, which are any areas where train movements may conflict with each other. They are either controlled by human operators or a computer, not the trains. Interlocking signals also tell operators which way points are set. The following interlocking signals are used on the TTC.

	Proceed, Points Set to Straight
	Proceed With Caution, Points Set to Straight
	Proceed With Caution, Points Set to Diverge
	Stop And Stay
	Call On (Train has been given permission to pass red signal)
	Entering Timed Block, Points Set to Straight
	Entering Timed Block, Points Set to Diverge
	Timed Block, timer has not yet run out (top red light flashes when timer is about to run out)