HUTT RAILWAY

Evening Post, Volume CXII, Issue 33, 9 February 1927, Page 10

HUTT RAILWAY

ELECTRIC SIGNALLING

AUTOMATIC LIGHT SYSTEM

The system of electric signalling to be used on the Hutt Valley railway is what is known as the three-coloured-light automatic. It will be put in over the whole of the three miles from the junction with the existing line to the Waterloo road station. The same system is installed'between Arthur's Pass and Eolleston on the Midland railway, on the Auckland section, and at Dunedin, but it was first installed on the Lamb ton-Lower Hutt section with the three-position semaphore arm. The basis of the system is the "track circuit," by which every part of the track is electrically alive. ' Power is fed at one end to the rails, ,flows thereon to the next signal, arid is then taken to a relay, the end portions of track between signals being insulated by wooden fishplates, and the rails from end to end being bonded together.

In the case of the new installation at the Hutt, coloured lights, red for danger, yellow for caution, and green for clear, will automatically tell the drivers the state of the line ahead and- behind. . '■■:?'■

Taking.three signals, A,B, and C: a train upon entering section A-B keeps A at danger as long as it occupies that section; upon passing signal B entering section B-C, signal B is kept at danger similarly to A as long as section B-C is occupied. The section A-B now being clear signal A operates to the caution position, being governed by the signal at B. Upon the train entering the third section (C —onwards) signal C is placed at danger and held so as in the former cases. Signal B operates to caution and A goes to "clear," giving the three p»sitions of "danger," "caution," and "clear" behind the train as it proceeds. It will be realised from this that according to the spacing of signals so can trains follow on. This sequence is identical both for double and single line working for following on movements.