Points Indicators - Rules

Mechanical Points Indicators operate in conjunction with Trap Points. The Indicators show a red square target when the trap points are in the derailing position and a purple square target when the trap points are reversed

This page explains the rules applying to points indicators. The mechanism of a points indicator is explained in my Structures pages.

Rule Book

Rule 50 from the 1965 Rule Book and an associated diagram explain points indicators. The 1943 Rule Book also mentions Points Indicators and the colour purple, which is many years before this colour was used at Track Warrant indicator loops.

50. (a) Trap points are derailing switches provided for the protection of the main line, crossing loop or other places as shown on S. and I. Diagrams. Except where instructions provide otherwise they must stand in the derailing position when not in actual use for passing traffic.
(b) A Points Indicator exhibiting a Red square target by day and a Red light by night when the points are in the derailing position, and a Purple square target by day and a Purple lignt by night when the points are reversed, is connected to and works with Trap points. (See Figs. 22 and 23 on page 118.)

Where movements over Trap points are authorised by Colour Light Shunting or colour-light signals Trap Points Indicators are not provided.

(c) Indicators referred to in the foregoing are provided solely for the purpose of indicating which way points lie, and the Engine Driver or Locomotive Assistant must observe the indication of indicators before a train or locomotive passes over the points. Where the movement is not controlled by a fixed signal a signal from the Signalman or Shunter must first be received; the Shunter must not give the signal until he has received the authority of the Signalman.

Note - Only at interlocked stations and at such other stations as are specified in train advices or working timetables will Points Indicators be fitted with lamps to give an indication by night.

In the 1988 Rule Book the rule is number 53. It contains the additional sentence "Trap Points Indicators at night may display a red reflectorised disc and a purple reflectorised disc in place of a red or purple light as the case may be." The 1988 rule uses the term Locomotive Engineer rather than Enginedriver. The diagram in the 1988 rule book is identical to the 1965 diagram.


Points Indicator and Trap Points at Trentham. The trap points are closed and the purple target is exhibited. The trap points are worked mechanically from the points motor of 18 points, out of sight on the right. 18 points are set for the straight through route, allowing an up train (towards the camera) to enter the single line. Note the electrical detector and facing points lock.   (23/9/01)

18 points at Trentham are set for the crossover so that a down train (away from the camera) can cross from the single line to the down main. The trap points are open and the points indicator has rotated so that red is displayed. The rod operating the indicator can be seen between the indicator and the electrical detector. Note that the "normal" position of 18 points is for the diverging route. (25/8/01)

A down EMU is crossing from the single line to the down main at 18 crossover, Trentham. The points indicator is exhibiting red, meaning that the trap points are open, protecting 18 crossover from vehicles in the loop (left).

The trap points probably no longer serve a useful purpose as the sidings off the loop were lifted a few years ago. Additionally, the need for a mechnical  points indicator is not obvious as the trap points are electrically detected and protected by 7 Down Starting From Loop, which is a stop & stay signal.  (25/8/01)

Another way of protecting the main line. This is the exit from the suburban platform at Upper Hutt. Safety points leading to the run-off road are worked by rodding from the main line points. Ground signal 54 Shunt and Down Starting From Suburban Platform authorises movement over the safety points. The running signal is 53 Down Starting From Main.  (23/9/01)

Last Updated: Thu Jul 6 11:29:12 NZST 2006