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Section 3; pages:
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2,
3,
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Section 3: Shunting Signals
(Page 3 of 4)
Certain shunting signals could legitimately be passed in the 'on' position. Typically, such signals controlled moves from a group of sidings onto a running line, but could be passed without being cleared if a shunting move was to be made into a headshunt. To help drivers identify the signals concerned, the MoT 'requirements' of 1925 encouraged the use of a yellow light in the 'on' position, and yellow colouring of the arm or face. A yellow indication in a shunting signal thus carries a quite different meaning than in a main signal (see Section 2). The Rule Book stated:
"Shunting signals showing a yellow arm or light may be passed, without being cleared, for movements in a direction for which the signal, when cleared, does not apply."
In the case of the earlier designs of shunting signals, where applicable their red lenses were replaced with yellow ones, and their red faces were simply re-painted yellow [3.43 - 3.45]. The 'off' indications remained as before.
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[3.43] Yellow Shunting Signal ('on').
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[3.44] Yellow Shunting Signal ('on').
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[3.45] Yellow Shunting Signal ('on').
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Where semaphore signals were involved, these were given a yellow lens, and a yellow arm having a black stripe [3.46 & 3.47].
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[3.46] Yellow Semaphore Shunting Signal ('on').
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[3.47] Yellow Semaphore Shunting Signal ('off').
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Miniature ground mounted semaphore signals were similarly altered [3.48 & 3.49].
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[3.48] Yellow Miniature Semaphore Shunting Signal ('on').
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[3.49] Yellow Miniature Semaphore Shunting Signal ('off').
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Where required, 'banner' shunting signals were given yellow arms [3.50 & 3.51] and disc signals were given yellow arms and lenses [3.52 & 3.53].
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[3.50] Yellow Banner Shunting Signal ('on').
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[3.51] Yellow Banner Shunting Signal ('off').
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[3.52] Yellow Disc Shunting Signal ('on').
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[3.53] Yellow Disc Shunting Signal ('off').
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As upper quadrant semaphore signals came to be generally introduced (see Section 2), miniature semaphore shunting signals working in the upper quadrant became standard (except on the Great Western Railway) [3.54 - 3.58]. There would however be no upper quadrant version of the miniature ground mounted semaphore signal.
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[3.54] Upper Quadrant Semaphore Shunting Signal ('off').
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[3.55] Upper Quadrant Yellow Semaphore Shunting Signal ('off').
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[3.56] Upper Quadrant Siding Signal ('off') (SR).
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[3.57] Upper Quadrant Siding Signal (with yellow lens) ('off') (SR).
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[3.58] Upper Quadrant Yellow Siding Signal ('off') (SR).
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In the earliest schemes where colour lights were used as main signals (e.g. Charing Cross/Cannon Street (Southern Railway), 1926 and Cardiff (Great Western Railway), 1933), shunting signals took the form of miniature colour lights. These showed a red light for 'stop' [3.59], or a green light for 'proceed' [3.60]. Certain signals were equipped with a yellow lens instead of the red [3.61]. These applied as per other types of yellow shunting signal, i.e. they could be passed, without being operated to the green aspect, for a movement in a direction for which the signal when operated to the green aspect does not apply.
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[3.59] Miniature Colour Light Shunting Signal ('on').
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[3.60] Miniature Colour Light Shunting Signal ('off').
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[3.61] Normally-Yellow Miniature Colour Light Shunting Signal ('on').
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Another form of shunting signal existed which had the same advantage as the miniature colour lights, i.e. they had no moving parts, but satisfied the recommendation that shunting signals should be of the 'position' type. Known as the 'position light' signal, they had been supplied by Westinghouse c.1928 for a resignalling scheme at Cape Town, South Africa. The LNER's resignalling between York and Northallerton in 1933 used identical position light signals. The 'stop' aspect was two white lights horizontally displayed [3.62], and the 'proceed' aspect was two white lights inclined upwards at 45° [3.63]. Thus the position of the lights corresponded to the angle of the stripe in disc or banner type shunting signals (see [3.29 & 3.30]).
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[3.62] Position Light Shunting Signal ('on').
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[3.63] Position Light Shunting Signal ('off').
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Normally it is the practice to clear any facing shunting signals in the route beyond a main signal when such main signal is cleared, so that the driver does not see a red light in the shunting signal. Since the position light signal did not show any red lights when 'on', it was considered acceptable not to clear the signal and allow it to be ignored when preceded by a main signal showing a main 'proceed' aspect. Position light signals associated with a main signal are not equipped to show an 'on' aspect, only being illuminated when the 'proceed' aspect is to be displayed (see [3.63]). An exception to this was where the associated position light signal was ground mounted. Originally, such signals could display an 'on' aspect.
Discussions on the standardisation of aspects in colour light signalled areas began in 1933, at the instigation of the Ministry of Transport. In May 1934, the sub-committee of the Railway Clearing House agreed that:
"... the use of signals of the colour-light type as ground shunt signals in colour-light areas, is undesirable and that signals of the 'position' type should be adopted as standard. The actual type to be used cannot at present be standardised."
One result of this recommendation was that miniature colour light shunting signals (see [3.59 - 3.61]) could no longer be used in new works. Illuminated disc or banner signals were acceptable, however they suffered the disadvantage of employing moving parts.
