Two Position & Three Position Signalling

The New Zealand railway system uses two-position and three-position signalling. Two-position is almost extinct. Two-position was usually associated with Tablet or Open Section working - both of which are obsolete. Three-position is currently used for automatic signalling.

This page describes two and three-position signalling as it is used in 2004. Two-position signalling is used at Masterton.

Two position signalling is almost extinct in 2004 - existing only at Masterton and Invercargill (1965 Rule Book).

Two & Three Position Signalling

Two Position
In two-position territory there are two types of signal - Home and Distant. The Distant acts gives warning of the indication shown by the Home and cannot display Stop. The Distant is not controlled by track circuits. The Home signal may or may not not be controlled by a track circuit. A station can be track circuited for other purposes.

Under Tablet working the rules required that for a non-stopping train the Home be placed at Clear-Proceed only when the tablet for the next section had been issued.

The Stop & Proceed concept does not apply in two-position territory.

(Above) Note that the Home signal does not automatically go to Stop behind 1601 (the 0825 Wellington Masterton passenger). Note also the absence of a marker.

Three Position
Three Position (or three-aspect) signalling combines the functions of Distant and Home into one signal. All signals are operated by track circuits and some are also under control of the signalman.

A fourth aspect - Advance Caution - has been added by flashing the yellow. Presumably a fifth aspect could be added by flashing the green, although I am not aware of any proposal to do this.

Additional aspects can be created by using combinations of vertically mounted lights.

Note - Do not confuse three-lens signals with three-aspect or multi-aspect signals.

Possible Confusion....

Safeworking Do not confuse the safeworking method on the single line between stations with two-position signalling. A signalled station can be an "island", with a variety of safeworking methods on either side - see the diagram on the right.

Automatic Operation Of Signals Some two-position signals went to Stop automatically when a train passed. For example, the mechanical Up Home at Upper Hutt was fitted with a reverser. Under Single Line Automatic working it would have been possible for a second up train to arrive at the Up Home before the signalman had placed it at Stop. This demonstrates that while two-position signals did not usually go to stop automatically, there is nothing inherent in two-position signalling that prevents it.

Point Indicator Loops. Points Indicators  used in Track Warrant territory are two-position. Note however that their indications are completely different from those of two-position signals - see TWC Regulations.

Masterton Photographs

Masterton R3 Up Distant. Note the absence of a marker light.   Photo Bruce Scott 2004.

Masterton 2 Down Home.   Photo Bruce Scott 2004.

Last Updated: Saturday, December 31, 2005

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