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Section 9: Signal Post Signs and Signals for Degraded Working

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Most signals, as well as displaying an aspect, are provided with signs or indicators that convey further information relevant to traincrews. Typically, this may include the signal number, identification of specific kinds of signals and information that relates to the provision and usage of a telephone or call plunger. The driver can use this information to determine which rules are applicable in situations such as being detained at the signal or during failure.


The majority of signs affixed to signal posts, or near signals, are of importance to drivers detained at the signal awaiting its clearance. In the old Rule Book, Rule 55 outlined the actions to be taken upon the detention of trains on running lines. This began:

"When a train has been brought to a stand owing to a stop signal being at Danger the Driver must sound the engine whistle, and, if still detained, the Guard, Shunter or Fireman must go to the signal box and remind the Signalman of the position of the train..."

At some locations, the walk from the signal to the signal box would have been time consuming or hazardous. This led the London & North Western Railway to devise the 'fireman's call box'. When the fireman pressed a plunger at the call box, an indicator in the signal box was operated. If the equipment had functioned correctly, a bell rang in the call box and the fireman was exempt from going to the signal box. The equipment was trialled in 1907, proved to be successful and rapidly spread to other parts of the LNWR. To indicate the presence of the fireman's call box, an illuminated sign with the appropriate words was provided [9.1].

[9.1] Fireman's Call Box Sign.
Area: LNWR   Usage: Medium   Status: Historical

At some signals, drivers were exempt from carrying out the requirements of Rule 55 on account of there being a track circuit or other form of train protection that would automatically indicate the presence of the train to the signalman. This was denoted by an illuminated sign fixed at or near the signal concerned, bearing the words "track circuit" [9.2], "train indicator in box" [9.3] or "Rule 55 exempt" [9.4].

[9.2] Track Circuit Sign.
Area: LNWR   Usage: Medium   Status: Historical
[9.3] Train Indicator Sign.
Area: GWR   Usage: Medium   Status: Historical
[9.4] "Rule 55 Exempt" Sign.
Area: L&YR   Usage: Medium   Status: Historical

The above signs were illuminated by a separate lamp provided in addition to the signal lamp. From 1912, the Midland Railway avoided the provision of separate lamps by fitting non-illuminated plates instead. The 'D' sign (so called because of its shape) [9.5] was introduced to denote that a fireman's call plunger was provided for the driver or fireman to remind the signalman of the presence of the train. W.C. Acfield designed the 'diamond' sign (actually an elongated hexagon) [9.6], which indicated exemption from Rule 55.

[9.5] 'D' Sign.
Area: Mid.R (subsequently All Areas)   Usage: High   Status: Historical
[9.6] Diamond Sign. Click Here for Photo
Area: Mid.R (subsequently All Areas)   Usage: High   Status: Current

On the Caledonian Railway, the presence of a track circuit was denoted by an indicator, in the shape of an elongated hexagon, fitted to the signal post. A purple light was displayed in the centre at night [9.7].

[9.7] Track Circuit Indicator.
Area: Cal.R   Usage: Low   Status: Historical

Since the advent of power signalling, it has been common practice for main and shunting signals within the areas concerned to be identified by plates bearing their identification. Signal identification plates vary in detail but are generally square or rectangular in shape and have either black characters on a white background or white characters on a black background [9.8]. Plates with a white background predominated at first, although the North Eastern Area of the LNER and its successor, the North Eastern Region of British Railways, favoured a black background. B.R. standardised on a black background for all signal identification plates in the mid 1970s. Current practice, originating from 1992, is to fit identification plates with a black background to all signals apart from shunting signals, which should have plates with a white background. Since the early 21st century, the provision of identification plates on signals in mechanically signalled areas has become commonplace; before then, such signals were usually referred to in driver/signalman communications by name only (e.g. "Up Outer Home").

[9.8] Signal Identification Plate.
Area: All Areas   Usage: High   Status: Current

Although they could be situated miles from the nearest signal box, the earliest automatic signals had not normally been provided with signal post telephones. The 'stop and proceed' rule was introduced in an effort to keep trains moving in the event of failure preventing an automatic signal from showing a 'proceed' aspect. This rule permitted drivers to pass an automatic signal displaying a 'danger' aspect on their own authority after waiting for a prescribed number of minutes and to proceed cautiously towards the next signal. Automatic colour light signals were originally identified by a plate bearing the letter "A" [9.9]. The 'stop and proceed' rule could also apply to semi-automatic signals while they were working automatically. Some semi-automatic signals had illuminated "A" signs [9.10], illuminated only when the controlling signal box was closed and indicating that the signal was working automatically. Both these signs were used on the LNER's Marylebone - Neasden scheme in 1923; however, the signal identification and "A" signs were combined onto a single plate [9.11]. On some later schemes, illuminated "A" signs were provided on both automatic and semi-automatic signals.

[9.9] "A" Sign.
Area: Various   Usage: High   Status: Historical
[9.10] Illuminated "A" Sign.
Area: Various   Usage: High   Status: Historical
[9.11] "A" Sign with Signal Identification.
Area: Marylebone - Neasden, LNER   Usage: Low   Status: Historical

The Great Western Railway introduced an experimental form of indicator in 1926, which was intended to replace the train indicator sign (see [9.3]) that needed its own separate source of illumination. The trial indicator comprised a stencil lettered "track", positioned immediately to the right of the signal lamp [9.12], by which it was illuminated in a similar manner perhaps to the Coligny-Welch lamps sometimes used to identify distant signals (see [2.62 - 2.65]). These indicators were not successful.

[9.12] "Track" Indicator.
Area: GWR   Usage: Low   Status: Historical

The LNER had adopted the diamond sign (see [9.6]) by 1926 and these were universally introduced to the LMS, the GWR and the SR in 1929. The 'D' sign (see [9.5]) was also universally adopted. The LNER was alone in using the 'D' sign to indicate the presence of a telephone at a signal, their original style of sign being shaped like a ring [9.13].

[9.13] 'D' Sign.
Area: LNER   Usage: High   Status: Historical

By 1927, the Southern Railway identified its signal post telephones by fitting diagonally striped signs to the cabinets that housed them [9.14]. Where a telephone was provided at the signal, the driver was required to wait for two minutes before using it to communicate with the signalman.

[9.14] Signal Post Telephone Sign.
Area: Southern Railway (subsequently All Areas)   Usage: High   Status: Current

Introduced by the LMS in 1932, a "T" sign at a signal denoted the presence of a telephone [9.15]. Where appropriate, the "T" sign could be combined with either a 'D' sign [9.16] or a diamond sign [9.17].

[9.15] "T" Sign.
Area: LMS (subsequently London Midland, Scottish and Western Regions)   Usage: High   Status: Historical
[9.16] Combined 'D' and "T" Sign.
Area: LMS (subsequently London Midland, Scottish and Western Regions)   Usage: Medium   Status: Historical
[9.17] Combined Diamond and "T" Sign.
Area: LMS (subsequently London Midland, Scottish and Western Regions)   Usage: High   Status: Obsolescent

The LMS devised illuminated versions of the diamond sign, "D" sign and "T" sign for use in tunnels and on underground railways. In each case, the relevant symbol was printed in red on a white circular background [9.18 - 9.20]. Where a "T" sign was combined with either a diamond sign or a "D" sign, a small black letter "T" was additionally placed in the centre of the sign [9.21 & 9.22].

[9.18] Illuminated Diamond Sign.
Area: LMS   Usage: Low   Status: Historical
[9.19] Illuminated "D" Sign.
Area: LMS   Usage: Low   Status: Historical
[9.20] Illuminated "T" Sign.
Area: LMS   Usage: Low   Status: Historical
[9.21] Illuminated Combined Diamond and "T" Sign.
Area: LMS   Usage: Low   Status: Historical
[9.22] Illuminated Combined "D" and "T" Sign.
Area: LMS   Usage: Low   Status: Historical