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Section 9: Signal Post Signs and Signals for Degraded Working

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The weakness with the 'stop and proceed' rule was the lack of distinction between an automatic signal held at 'danger' owing 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 [9.26]. 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 LMS fitted "P" signs to a number of signals on the electrified line between Barking and Upminster in March 1937. 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 on 26 November 1947, the MoT recommended that the Southern Region (as successor to the Southern Railway) should install "P" signs at its semi-automatic signals. In October 1948, however, British Railways' Operating Committee recommended the removal of "P" signs from all signals. This was agreed to by the MoT in March 1949, subject to a telephone being provided at every signal from which there was no easy access to a continuously manned signal box.

[9.26] "P" Sign.
Area: SR / LNER / LMS   Usage: High   Status: Historical

By 1936, signs of a new design had been introduced for the identification of automatic and semi-automatic signals. The automatic signal plate bears a black horizontal band across the width of a white background [9.27]. The semi-automatic signal plate additionally has the word "semi" above the black band [9.28]. These signs may incorporate the signal's identification number [9.29 & 9.30].

[9.27] Automatic Signal Plate. Click Here for Photo
Area: All Areas   Usage: High   Status: Obsolescent
[9.28] Semi-Automatic Signal Plate. Click Here for Photo
Area: All Areas   Usage: High   Status: Obsolescent
[9.29] Automatic Signal Plate with Signal Identification.
Area: All Areas   Usage: High   Status: Obsolescent
[9.30] Semi-Automatic Signal Plate with Signal Identification.
Area: All Areas   Usage: High   Status: Obsolescent

On the Cheshire Lines Committee, and later the London Midland Region, the signal identification was frequently incorporated onto a diamond sign, where one was provided [9.31]. If the signal identification was incorporated onto a combined diamond and "T" sign, the "T" was printed in outline [9.32] to avoid it being mistaken as part of the signal identification.

[9.31] Diamond Sign with Signal Identification.
Area: CLC (subsequently London Midland Region)   Usage: High   Status: Obsolescent
[9.32] Combined Diamond and "T" Sign with Signal Identification. Click Here for Photo
Area: London Midland Region   Usage: High   Status: Historical

The Scottish Region of British Railways, having been formed of parts of the former LMS and LNER, had inherited both companies' methods of indicating the provision of a telephone at a signal. The former LMS practice of fitting a "T" sign (see [9.18]) or a diamond sign with the letter "T" (see [9.20]) became standard on the Scottish Region in preference to the LNER's 'D' sign (see [9.6]). The Western Region chose to adopt the former LMS practice in 1954.


On the Scottish Region, when a "T" sign (see [9.18]) was required at a position light shunting signal (see Section 3), it could be combined with the identification plate. Where the signal identification was in white characters on a black background, the "T" sign was often similarly coloured [9.33].

[9.33] "T" Sign.
Area: Scottish Region   Usage: Medium   Status: Historical

Drivers operating over lines worked by the Absolute Block system need to know the locations of any intermediate block signals to enable the applicable rules to be carried out at them. The locations of these signals were therefore detailed in the Sectional Appendices. From 1961, intermediate block home signals were being fitted with a plate bearing a vertical black band on a white background [9.34] to make them readily identifiable to drivers. In some instances, the signal number was incorporated onto the plate [9.35].

[9.34] Intermediate Block Home Signal Plate.
Area: All Areas   Usage: High   Status: Current
[9.35] Intermediate Block Home Signal Plate with Signal Identification.
Area: All Areas   Usage: Medium   Status: Obsolescent

The signs used to denote the provision of a telephone at a signal were standardised by British Railways in January 1962. The former disparate practices of fitting a "T" sign (see [9.18]) or a diamond sign with the letter "T" (see [9.20]) on the London Midland, Scottish and Western Regions and a 'D' sign (see [9.6]) on the Eastern and North Eastern Regions were discontinued, and gradually over a number of years these signs were removed from signals. The signal post telephones continued to be identified by the black and white diagonally striped sign (see [19.1]), and in some cases a similar sign was also attached to the signal [9.36]. Plain white diamond signs (see [9.7]) ceased being fitted to signals at which a telephone was provided but were otherwise applied as before.

[9.36] Signal Post Telephone Sign.
Area: All Areas   Usage: High   Status: Current

The method of indicating exemption from Rule 55 at shunting signals was standardised in 1962. In the case of a disc shunting signal (see [3.45] and [3.79]), a white diamond sign (see [9.7]) of miniature size was to be superimposed on the red band on the face of the disc [9.37]. Signals consisting of more than one disc for route indication purposes (see Section 6) were provided with a diamond sign on each disc. Position light shunting signals (see [3.86]) were to be exempted by a Rule Book instruction, obviating the fitment of diamond signs.

[9.37] Diamond Signs on Disc Shunting Signals ( (a) - single disc; (b) - stacked discs (e.g. three-tier) ). Click Here for Photo
Area: All Areas   Usage: High   Status: Uncertain

A signal post telephone situated between two lines poses a specific safety risk to users. A train driver who has left the driving cab to use the telephone is protected from train movements on one line by the presence of the stationary train but may be at danger from trains passing on the adjacent line if clearances are restricted. In 1983 and 1984, a number of signals in the south of London were fitted with a white diamond sign bearing a letter "T" (see [9.20]) to remind drivers that they need not go to the telephone if detained at the signal. If the signalman needed to speak with the driver, a white flashing light was exhibited within the sign [9.38] to call the driver to the telephone.

[9.38] White Diamond Sign with "T" and White Flashing Light.
Area: Southern Region   Usage: Low   Status: Historical

In July 1984, a signal post telephone at Clapham Junction was replaced with a loudspeaking telephone for trial purposes. The driver can normally remain in the driving cab and speak through an opened window while using this kind of telephone. The signal involved, number VC610, had previously been fitted with a diamond sign as described above (see [9.38]), and for the trial (which lasted nearly three years), the white flashing light in this sign was taken out of use, a light with a similar function being incorporated on the new telephone instrument.

When a train was detained at a signal provided with a signal post telephone, the rules ordinarily required the driver to contact the signalman after waiting for two minutes. In 1987, signal post telephone signs incorporating a numeral [9.39] 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, if at variance with the standard time.

If the striped sign bears a numeral "0" [9.40], the driver must immediately contact the signalman when the train is detained at the signal. These 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.

[9.39] Signal Post Telephone Sign (e.g. initial contact to be made after a five minute delay).
Area: All Areas   Usage: Medium   Status: Current
[9.40] 'Zero Minutes' Plate. Click Here for Photo
Area: All Areas   Usage: High   Status: Current

1987 saw the introduction of new standard signs for use at signals where, owing to restricted clearance from an adjacent line, the driver need not remind the signalman of the presence of the train when detained there. The signals concerned were to be fitted with diamond signs coloured yellow. A letter "T" on the diamond sign [9.41] denoted the provision of a telephone with a call back facility, whereas a letter "L" [9.42] denoted that a loudspeaking telephone was provided. In either case, the driver was required to communicate with the signalman when the associated white flashing light was exhibited [9.43]. By 1993, loudspeaking telephones were no longer being installed.

[9.41] Yellow Diamond Sign with "T".
Area: All Areas   Usage: Medium   Status: Historical
[9.42] Yellow Diamond Sign with "L".
Area: All Areas   Usage: Medium   Status: Historical
[9.43] White Flashing Light (e.g. signal provided with loudspeaking telephone).
Area: All Areas   Usage: Medium   Status: Obsolescent

From 1992, yellow diamond signs bearing the letter "X" [9.44] were provided at certain signals to indicate that the signal post telephone, which is located in an area of limited clearance, must not be used, except in an emergency. 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 cabinets concerned were fitted with a sign bearing a yellow roundel superimposed on a black cross (see [19.11]).

[9.44] Yellow Diamond Sign with "X". Click Here for Photo
Area: All Areas   Usage: Medium   Status: Obsolescent

A potential hazard was revealed when a colour light signal fitted with a yellow diamond sign and displaying a single yellow aspect (see [2.106]) was mistaken by a driver as a double yellow aspect (see [2.108]). Consequently, it was decided that diamond signs should not have a yellow background, and diamond signs bearing the letters "T" (see [9.20]), "L" or "X" [9.45 & 9.46] had a white background from 1995 onwards.

[9.45] White Diamond Sign with "L".
Area: All Areas   Usage: Medium   Status: Obsolescent
[9.46] White Diamond Sign with "X". Click Here for Photo
Area: All Areas   Usage: High   Status: Current