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Section 9: Signal Post Signs and Signals for Degraded Working

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In 1933, the LNER installed colour light signals between York and Northallerton. All the main signals, apart from junction signals, were provided with some form of auxiliary light to locate the signal in the event of the main signal light failing. In the case of automatic signals, the illuminated "A" sign (see [9.8]) acted as the auxiliary light. Controlled signals were fitted with a plain white auxiliary light that would be illuminated only if the main aspect failed [9.24]. Semi-automatic signals had both an illuminated "A" sign and a plain white auxiliary light, the latter being provided for use when the signal was not working automatically. The junction signals had multiple signal heads (see [6.22]) and so did not require to be fitted with auxiliary lights.

[9.24] Auxiliary Light (LNER).

The weakness with the 'stop and proceed' rule was the lack of distinction between an automatic signal held at 'danger' due to failure and one correctly showing 'danger' because another train was in the section ahead. Applying the rule in the latter scenario would result in two trains occupying the same section, contrary to the fundamental principle of the space interval system. Following accidents in 1933 and 1934 in areas of automatic signalling, a review of the 'stop and proceed' rule was undertaken. As a result, it was decided that telephones should be provided at automatic signals so that permission to pass them at 'danger' could be given by the signalman. To avoid the risk of a verbal instruction being misunderstood, the Ministry of Transport also recommended the provision of "P" ('proceed') signs on the signals [9.25]. When switched on by the signalman during a failure, an illuminated "P" sign was visual authority to pass the signal concerned at 'danger' and to proceed cautiously towards the next signal. If the "P" sign was already lit when the train arrived at the signal, the driver was required to wait for three minutes before proceeding with caution. "P" signs were in use on the Southern Railway from 1936 and on the LNER by 1939. The Southern Railway installed "P" signs only at automatic signals whereas the LNER provided them also at semi-automatic signals. Following an accident at Farnborough in 1947, the MoT recommended that the Southern Region (as successors to the Southern Railway) should install "P" signs at its semi-automatic signals.

[9.25] "P" Sign.

By 1936, signs of a new design had been introduced for the identification of automatic [9.26] and semi-automatic signals [9.27]. These signs may incorporate the signal's identification number [9.28 & 9.29].

[9.26] Automatic Signal Plate.	[9.27] Semi-Automatic Signal Plate.


[9.28] Automatic Signal Plate with Signal Identification.	[9.29] Semi-Automatic Signal Plate with Signal Identification.

A sign was introduced c.1961 to identify an Intermediate Block Home signal [9.30]. The signal number may be incorporated onto the sign [9.31].

[9.30] Intermediate Block Home Signal Plate.	[9.31] Intermediate Block Home Signal Plate with Signal Identification.

From 1962, the practice of fitting a "T" sign (see [9.15]) or a diamond sign with the letter "T" (see [9.17]) to a signal to denote the provision of a telephone was discontinued. The signal post telephone would continue to be identified by the black and white diagonally striped sign (see [9.14]). Concurrent with that change, a new sign with a St. Andrew's cross was introduced [9.32]. This would be used to distinguish lineside telephones not at signals or telephones at signals where Rule 55 did not apply (e.g. signals not on running lines or loops).

[9.32] Telephone Sign.

When a driver was detained at a signal bearing a black and white diagonally striped sign (see [9.14]), the rules normally required that he contact the signalman after waiting two minutes (this was varied to three minutes on the Southern Region). In 1987, signal post telephone signs incorporating a numeral [9.33] were introduced at certain signals. The numeral indicates the number of minutes that the driver should wait before contacting the signalman when detained at the signal, when at variance with the standard time.

If the striped sign bears a numeral "0" [9.34], the driver must immediately contact the signalman when the train is detained at the signal. Such signs may be exhibited at signals temporarily during times of severe disruption. Some are permanently fitted to the signal post but are folded shut when not in use. A driver may be instructed by the signalman to open the sign.

[9.33] Signal Post Telephone Sign (e.g. initial contact to be made after a five minute delay).	[9.34] 'Zero Minutes' Plate.

Concerns for the safety of staff using signal post telephones at locations where there is limited clearance from an adjacent line prompted the introduction of new procedures for using such telephones. 1987 saw the introduction of diamond signs coloured yellow and bearing either the letter "T" or "L" [9.35 & 9.36]. Where either sign is provided, the driver need not remind the signalman of the presence of the train when detained but must communicate with the signalman when the associated white flashing light is exhibited [9.37]. The telephones at these signals have a call back facility. Where the signal has a diamond sign bearing the letter "L", this indicates that a loudspeaking telephone is provided. Use of this type of telephone does not normally require the driver to leave the driving cab. By 1993, loudspeaking telephones were no longer being installed.

[9.35] Yellow Diamond Sign with "T".	[9.36] Yellow Diamond Sign with "L".	[9.37] White Flashing Light (e.g. signal provided with loudspeaking telephone).

From 1993, yellow diamond signs bearing the letter "X" [9.38] were provided at certain signals. This sign indicates that the signal post telephone must not be used (except in an emergency) due to it being located in an area of limited clearance. Communication with the signalman must normally be by radio equipment unless the driver has been informed that it is safe to use the telephone. The telephone cabinet was given a special sign bearing a yellow roundel superimposed on a black cross [9.39] instead of the usual black and white diagonally striped sign (see [9.14]).

[9.38] Yellow Diamond Sign with "X".	[9.39] Signal Post Telephone Sign - Limited Clearance.

A potentially unsafe situation was revealed when a colour light signal fitted with a yellow diamond sign and displaying a single yellow aspect (see [2.93]) was mistaken by a driver as a double yellow aspect (see [2.95]). To avoid a recurrence, it was decided that diamond signs should not have a yellow background and in future (from 1995) there would be a white background on diamond signs bearing the letters "T" (see [9.17]), "L" or "X" [9.40 & 9.41].

[9.40] White Diamond Sign with "L".	[9.41] White Diamond Sign with "X".

Also in 1995, the sign fitted to telephone cabinets located in areas of restricted clearance (see [9.39]) was altered. The yellow roundel was retained but the St. Andrew's cross was replaced by diagonal stripes [9.42], this being more appropriate for a signal post telephone.

[9.42] Signal Post Telephone Sign - Limited Clearance.

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