Ngauranga To Wellington

The Ngauranga to Wellington section has some interesting examples of New Zealand Double Line Automatic Signalling practice, including:

  • Approach Controlled low-speed lights allow trains to safely stack up without the intervention of the signalman.
  • Two methods of permissive working - Stop & Proceed signals and low-speed lights.
  • Advance Caution indication
  • Train Stops
  • A-Lights

Down Outer Home Approach signal A2R (from Hutt).

  Ngauranga - Kaiwharawhara   Kaiwharawhara - Wellington   Photographs  

Ngauranga To Kaiwharawhara

Advance Caution 6R and 2R can display Flashing Yellow over Red - Advance Caution. This indicates that two sections ahead are clear and that the second signal ahead is at Stop. The down main is next to the sea and in southerly conditions waves land on the track, making stopping and starting dfificult.

Single Unit Intermediate Signals 337 is a single unit intermediate (automatic) signal confgured for Stop & Proceed operation.

Normal Position of Signals 337 is an automatic Stop & Proceed signal so is Normal Clear. 293 is Nomal Caution because A2R is Normal Stop. 2R (not shown), which is in advance of approach signal A2R, is Normal Stop so A2R is also Normal Stop. 2R is Normal Clear if Ngauranga is switched out and Normal Stop if switched in.

Train Stops When A2R is at Stop the train stop arm is raised. If an EMU passes the signal at stop a lever on the EMU is tripped, applying the brakes.

Double Unit Intermediate Signals Signal 673 is an intermediate (automatic) signal configured as a Stop & Proceed. It has two units because before the loop was lifted the signal could display yellow over green - Approach Medium Speed.

Switch Out 2R is a double unit Stop & Stay signal. The illuminated A-light indicates that the down main is switched out and 2R Stop & Proceed rules apply to the signal. Before the loop was lifted 2R could display red over green - medium speed.

Signal Numbering Intermediate signal 673 is 6.73 km (rounded to 10m) from the reference point. On the up main intermediate signals have even numbers. Signal 2R is controlled and reads from left to Right on the panel. There are various schemes for the numeric part of the number. Approach signal A2R operates automatically but depends on 2R, a controlled signal in advance (not shown)

Nomenclature 2R is a Home signal, 6R a Directing signal and 10R a Starting signal. The term Directing may be unique to New Zealand - in this instance 6R is equivalent to an Inner Home.

Kaiwharawhara To Wellington

Approach Control Is used to control the speed of approaching trains. Using A2R and 2R as and example:- If D3 is not occupied and 2R is at Stop the approach signal A2R will also display Stop. When a train occupies D4 signal A2R will clear to yellow after a time delay of x seconds. If a train approaches the signal too fast the brakes will be tripped by the raised trainstop. If 2R is indicating yellow or green then A2R behaves as an automatic signal.

If D3 is occupied then A2R will display Stop. When D4 is occupied the low-speed light on A2R will be illuminated after an x second time delay. The same applies to A4R/4R and A39/39.

Low-Speed Lights The low-speed light on 39 Down Home can be turned on by the signalman to authorise a movement into an occupied track or a track suitable for low-speed only.

Searchlight Signals are installed at the station throat. In 2003 several searchlight mechanisms were replaced with three-colour units.

Approach Locking of signals ensures safety should a signal be put to Stop in the face of an on coming train. At Wellington Junction 2R and 4R are both approach locked. For example, assume that 2R is indicating Clear Proceed and a train is on the approach track D3. If the signalman places 2R to Stop 3 points will remain locked for 90 seconds. This gives the train time to either stop or to occupy the points track circuit (and hence lock the points).

Approach Cleared Low-Speed Lights The low-speed lights on the approach signals A2R, A4R and A39 allow trains to stack up without the intervention of the signalman in A-Box.

For example, assume that a train is stopped at 2R. A second train approaching on D4 will receive a low-speed light on A2R after a time delay of x seconds. The second train can then draw cautiously up to the rear of the first train. This movement does not reqire the authority of the signalman.


The quality of some of these photos is degraded, partly because of problems with my scanner.

Double unit Stop & Proceed automatic signal 673 approaching Ngauranga. This signal can display yellow over green (approach medium speed).

Note the rectangular sighting background and compare it with the photograph on the right.

2R Down Home at Ngauranga is controlled by the signalman, A-Box. The A-light is illuminated which means that the Down Main is switched out - the signal operates automatically and Stop & Proceed rules apply. The signal can display Advance Caution (flashing yellow over red) and Medium Speed (red over green). Medium Speed is for moves on to the up main, which is signalled for bi-directional working through Ngauranga station.

411 automatic signal. The offset marker indicates that this is a Stop & Proceed Signal. (Automatic signals can be either Stop & Proceed or Stop & Stay).

A2R Down Home Approach from Hutt on the left with A4R Down Home Approach from Tawa on the right. These signals are not controlled by the signalman. Note the train stop in the raised position.

2R Down Home from Hutt on the left with 4R Down Home from Tawa on the right. These signals are controlled by the signalman - including the low-speed lights.

A39 Down Home Approach with an illuminated low-speed light. The upper unit is displaying Red (not visible in photo). The low-speed light is approach cleared.

39 Down Home From Main (left) from an unusual perspective. We are running wrong line (on verbal authority of the signalman) on the up main. The signal on the right is 38 Down Home from Johnsonville.

Train Stop The train stops at Kaiwharawhara are in a dangerous location and could be photographed only by trespassing. This photograph is therefore of a train stop on the Melling Branch.

Last Updated: Sat Dec 16 09:11:55 NZDT 2006

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