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Section 2: Main Signals

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In a semaphore signalling area, lack of space could prevent a particular signal from being fitted with a semaphore arm. The arm in this instance was dispensed with, and the signal conveyed its indications by just a red or green light by day and night. The signals concerned were usually provided with intensified lighting, which produced a beam of light equivalent to a colour light signal. Although semaphore signalling practice permits a green light in one stop signal to be followed by a red light in the next, this sequence cannot normally occur in standard colour light practice. Where the LMS considered that drivers might confuse the armless signal with a normal colour light signal and wrongly take the green aspect as an indication that the next signal was also 'off', a special marker was provided. Exhibiting a black ring on a white opal background [2.125], the marker was illuminated only when the signal it was fitted to was exhibiting a green aspect and, where practicable, only if the signal ahead was at 'danger'. The lit marker advised the driver that the signal was acting like a semaphore signal, and the next signal may be at 'danger'.

[2.125] Green Aspect with Illuminated Marker below.
Area: LMS   Usage: Low   Status: Historical

To accommodate increased wartime traffic, the GWR provided intermediate block sections through the Severn Tunnel in November 1941. The intermediate block home signal on each line took the form of a two-aspect colour light signal. As a precaution against lamp failure, the 'danger' aspect consisted of two red lights [2.126]. These signals were removed in May 1947.

[2.126] Double Red Aspect.
Area: Severn Tunnel / South London   Usage: Low   Status: Historical

Two signs were installed between Wolverhampton Steel Terminal and Wednesbury Central (London Midland Region) in 1973 to act as distant marker boards for a stopping point beyond. Both signs were in the form of 'intermediate boards' (see [16.19]), which were usually intended for use on approach to a level crossing where trains are required to stop.

On 28 February 1975, an accident occurred at Moorgate on the Northern City Line, which was then part of the London Underground. A loaded passenger train ran at speed through the buffer stop and into the tunnel end wall. As a result, British Rail decided that in future all colour light signals reading into terminal platform lines would show a yellow rather than a green aspect when the line was clear to the buffer stop.

In December 1975, the yellow aspect (see [2.106]) of the single-aspect colour light distant signal on the Gravesend West branch at Fawkham Junction (Southern Region) was replaced by a yellow fluorescent disc on the existing signal post [2.127].

During bridge construction work on the Riverside branch (Newcastle) in February 1977, the site of the work was protected in each direction by a stop board reading "Stop - Await instructions" (see Section 26). An advance warning board comprising a yellow disc on a white background [2.128] was provided on the Up Branch line to act as a fixed distant signal for the stop board ahead.

[2.127] Fixed Distant Marker.
Area: Fawkham Junction   Usage: Low   Status: Historical
[2.128] Advance Warning Board.
Area: Riverside branch (Newcastle)   Usage: Low   Status: Historical

In May 1977, the single line through Kirkby station (London Midland Region) was divided by the installation of back-to-back buffer stops to form two terminating branch lines. A marker board was provided on the approach to each buffer stop, and although these performed the function of a fixed distant signal, they took the form of advance warning boards of the style more usually associated with level crossings (see [16.15]). A similar board was installed on the approach to the buffer stop at Blackpool South station in March 1982. Both boards at Kirkby were replaced by standard reflectorised distant boards in December 1985.

The Liverpool Loop line, opened in May 1977, was provided with two-aspect signalling similar to that which was already in widespread use on the London Underground. Two-aspect signalling involves two types of signals, i.e. stop signals and repeater signals. A stop signal shows a red light for "danger - stop" or a green light for "clear - proceed". Where sighting is good, drivers are expected to be able to stop at a 'danger' signal with no advance warning. Where sighting of a stop signal is restricted, a repeater signal will be provided in rear. A repeater signal shows a yellow light for "caution - be prepared to find next signal at danger" or a green light for "clear - proceed". A repeater signal for a stop signal in advance may be co-located with the preceding stop signal. Where this occurs, the repeater signal is mounted below the stop signal, so that the 'caution' aspect comprises a green light over a yellow light [2.129], and the 'clear' aspect is green over green [2.130]. When the stop signal is displaying a red aspect, no light is shown in the repeater signal below, in contrast to the 'danger' aspect displayed by earlier combined stop and distant signals comprising separate colour light heads (see [2.109]).

[2.129] Green Aspect over Yellow Aspect.
Area: Liverpool Loop line   Usage: Low   Status: Current
[2.130] Green Aspect over Green Aspect.
Area: Liverpool Loop line   Usage: Low   Status: Current

Originally, no warning was provided to drivers on the approach to terminal stations worked by the One Train Working method (where signals were not needed), except at a few places where signs normally meant for other purposes had been misappropriated to act as marker boards (see above). In 1977, a new board was proposed for use in such situations, comprising a black diamond on a white reflectorised background [2.131]. Self-luminous 'Betalight' strips could be fitted if necessary.

[2.131] Terminal Station Board ( (a) - reflectorised; (b) - with Betalight strips ).
Area: Unknown   Usage: Nil   Status: Historical

With the introduction of the Class 253 and 254 'High Speed Trains' (or 'InterCity 125s') to British Rail, it was found necessary to introduce two additional signal aspects. The new flashing aspects were designed to give the driver advance warning that the junction signal ahead (see Section 6) is showing a 'proceed' aspect applicable to the diverging route. Where there is more than one diverging route, the flashing aspects only refer to the highest speed divergence(s). A flashing single yellow aspect [2.132] means "preliminary caution - be prepared to find the next signal displaying one yellow light, with a route indication for the highest speed diverging route". Where provided, the flashing double yellow aspect [2.133] means "proceed - next signal displaying flashing single yellow" and is an indication of a diverging route ahead of the next but one signal. The new aspects were first introduced at Didcot East Junction (Western Region) in March 1979, signals R70 and DM49 on the Down Main line being equipped to display a flashing single yellow and a flashing double yellow aspect, respectively. This installation was soon followed by others on each of the remaining regions apart from, initially, the Southern Region.

[2.132] Flashing Single Yellow Aspect.
Area: All Areas   Usage: High   Status: Current
[2.133] Flashing Double Yellow Aspect.
Area: All Areas   Usage: High   Status: Current

In November 1979, a marker board was erected on the approach to the buffer stop at Stourbridge Town station (London Midland Region). Acting as a fixed distant signal, the board displayed an outline of a semaphore distant arm in the 'on' position [2.134].

Between 1980 and 1982, distant boards were being provided in place of fixed semaphore distant signals on various colliery branch lines on the Eastern Region. These comprised a square yellow board with a black chevron [2.135].

[2.134] Distant Board.
Area: Stourbridge Town   Usage: Low   Status: Historical
[2.135] Distant Board.
Area: Eastern Region   Usage: Medium   Status: Historical

An experimental form of distant board appeared at Blaenau Ffestiniog (London Midland Region) c.1981, on the single line from Trawsfynydd. The board had the image of a yellow distant arm on a black background, and three self-luminous 'Betalights' were fitted across the arm to give drivers a visible indication during darkness [2.136]. Betalights had the drawbacks of being radioactive and susceptible to vandalism.

[2.136] Distant Board with Betalights.
Area: Blaenau Ffestiniog   Usage: Low   Status: Historical

In the early 1980s, a 'low cost signalling committee' was formed, tasked with developing proposals aimed at reducing the cost of signalling lightly used lines. Amongst other ideas, these included the emergence of a standard form of reflectorised distant board, following the manufacture of a number of experimental boards for evaluation purposes [2.137 - 2.140]. The style of board that was chosen to become standard [2.140] was first put into use in 1982.

[2.137] Experimental Reflectorised Distant Board.
Area: Unknown   Usage: Nil   Status: Historical
[2.138] Experimental Reflectorised Distant Board.
Area: Unknown   Usage: Nil   Status: Historical
[2.139] Experimental Reflectorised Distant Board.
Area: Various   Usage: Low   Status: Obsolescent
[2.140] Experimental Reflectorised Distant Board (subsequently adopted as standard). Click Here for Photo
Area: All Areas   Usage: High   Status: Current

A new signal aspect was introduced to facilitate special test runs of the new Class 91 electric trains on the East Coast Main Line at speeds of up to 140 mph. Most of the signals on the Fast lines between Peterborough and Stoke Tunnel were altered in May 1988 to be capable of displaying a flashing green aspect [2.141]. For the test trains, a flashing green aspect gave authority to exceed 125 mph, and a steady green aspect (see [2.107]) meant "reduce speed to 125 mph". For all other trains, a flashing green aspect has the same meaning as a steady green.

[2.141] Flashing Green Aspect.
Area: Peterborough - Stoke Tunnel   Usage: Medium   Status: Obsolescent

In the South London area in 1992 and 1993, while resignalling work was being carried out in connection with the Channel Tunnel project, temporary block working by ticket was implemented over certain lines. The colour light signals at the exits from the affected sections were fixed at 'danger', and a handsignalman appointed at each would instruct the driver to proceed when authorised by the signalman. Because the signals in question had no lamp-proving, their 'danger' aspect comprised two red lights (see [2.126]). In the event of one light failing, the handsignalman would immediately inform the signalman.