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Section 18: Signs in Electrified Areas

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Mainline railway electrification in Great Britain has its origins in the early 20th century. The first electrification schemes supplied DC traction energy to trains, at a variety of different voltages, along either conductor rails or overhead lines. In 1956, British Railways adopted the French 25 kV AC overhead method of electrification as standard for future work, apart from extensions to other existing systems. A lower voltage of 6.25 kV was originally employed in built-up suburban areas, which was later converted to the standard 25 kV. Electrification telephone signs are covered in Section 19.


The North Eastern Railway had electrified some railways around Tyneside in 1904 on the 600 V DC third rail system. Drivers of electric trains were required to shut off the power after reaching full speed and allow the train to coast as much as possible. A diamond shaped board with a red border [18.1] was installed at the point where the power should normally be switched off, under normal conditions with a fully loaded four-coach train. A diamond shaped board with a green border [18.2] marked the point where the power could be switched on again.

[18.1] 'Switch Power Off' Board.
Area: NER   Usage: Unknown   Status: Historical
[18.2] 'Switch Power On' Board.
Area: NER   Usage: Unknown   Status: Historical

A unique feature of the colour light signalling introduced on the Watford 'New' Line in 1932/1933 was the automatic placing to 'danger' of signals to protect a section in which the current had been cut off. This also caused the illumination of an indicator reading "track dead" [18.3] on the post of each protecting signal. The driver was required to stop and telephone the signalman if a "track dead" indicator was lit.

On lines electrified with conductor rails, flood indicators were installed at some places particularly susceptible to flooding. On the Watford 'New' Line, flood indicators were provided on the approaches to Harlesden Long Bridge in October 1957. In the event of flood water reaching the top of the running rails, the indicators were illuminated, each displaying the word "flood" [18.4], and the protecting signals were automatically placed or maintained at 'danger'.

[18.3] "Track Dead" Indicator.
Area: Watford New Line, LMS   Usage: Medium   Status: Historical
[18.4] Flood Indicator.
Area: Harlesden Long Bridge   Usage: Low   Status: Historical

Boards with the words "section gap" [18.5] were provided on the DC electrified lines of the London Midland Region to mark the locations of substation section gaps, where the conductor rails are gapped.

[18.5] "Section Gap" Board.
Area: Watford New Line / North London Line / Liverpool area   Usage: Medium   Status: Historical

For staff safety reasons, some goods yards in the Southern Region were provided with overhead wires in the late 1950s. This enabled DC locomotives fitted with pantographs to shunt in these yards without the need for a third rail. The point where the pantograph had to be raised or lowered was marked by an illuminated sign, which had a letter "R" on one side ('raise pantograph') [18.6] and an "L" on the other side ('lower pantograph') [18.7].

[18.6] 'Raise Pantograph' Sign.
Area: Southern Region   Usage: Low   Status: Historical
[18.7] 'Lower Pantograph' Sign.
Area: Southern Region   Usage: Low   Status: Historical

Lineside warning signs are erected on the approach to overhead electrified lines. The original style of warning sign had a 'flash' symbol and an upward pointing arrow in red on a white background [18.8]. The rear of the sign may be painted with green and white diagonal stripes [18.9].

[18.8] Warning Sign at Entrance to Overhead Electrified Area.
Area: All Areas   Usage: High   Status: Obsolescent
[18.9] Sign denoting Exit from Overhead Electrified Area.
Area: All Areas   Usage: High   Status: Obsolescent

A later design of warning sign for overhead electrified lines has a double flash symbol [18.10]. This sign has occasionally also been used away from overhead electrified areas to denote power lines crossing over the railway. A similar sign, with the words "live rails", may be used to denote the approach to an area of third rail electrification [18.11].

[18.10] Warning Sign at Entrance to Overhead Electrified Area.
Area: All Areas   Usage: High   Status: Obsolescent
[18.11] Warning Sign at Entrance to Third Rail Electrified Area.
Area: All Areas   Usage: Medium   Status: Obsolescent

Some of the original circular "track dead" indicators and flood indicators on the Watford New Line (see [18.3 & 18.4]) were renewed as stencil indicators that displayed the same words when illuminated [18.12 & 18.13].

[18.12] "Track Dead" Indicator.
Area: Watford New Line   Usage: Low   Status: Historical
[18.13] Flood Indicator.
Area: Harlesden Long Bridge   Usage: Low   Status: Historical

In November 1984, a flood indicator in the form of a miniature colour light signal was provided at the east end of Silvertown Tunnel on the North Woolwich line. Normally a white aspect was displayed [18.14], but in the event of flooding, a red aspect was displayed [18.15]. A similar flood indicator was installed on the adjacent goods line in September 1985, both indicators working simultaneously.

[18.14] Flood Warning Signal (normal aspect).
Area: Silvertown Tunnel   Usage: Low   Status: Historical
[18.15] Flood Warning Signal ('stop' aspect).
Area: Silvertown Tunnel   Usage: Low   Status: Historical

The Romford to Upminster branch (Eastern Region) was electrified with the 25 kV AC overhead wire system in 1986. Owing to restricted clearances below two overbridges between Romford and Emerson Park stations, 'dead' sections were provided in the overhead wire, through which electric trains are required to coast. Notice boards bearing the letters "D" and "T" were installed to denote the commencement and termination, respectively, of each dead section [18.16 & 18.17].

[18.16] Dead Section Commencement Board.
Area: Romford - Emerson Park   Usage: Low   Status: Uncertain
[18.17] Dead Section Termination Board.
Area: Romford - Emerson Park   Usage: Low   Status: Uncertain

On the DC electrified lines in the Liverpool area, special arrangements exist to advise drivers during times of reduced power supply. During periods when it is necessary to reduce electrical loading on the system, a board bearing a large letter "E" in yellow on a black background [18.18] will be exhibited at the stopping point of each station within the affected section. The sign indicates to the driver that the 'series' position of the controller must be used until a station is reached where an "E" board is not exhibited.

[18.18] "E" Board.
Area: Liverpool area   Usage: Medium   Status: Current

On AC electrified lines, a neutral section is a short earthed section of overhead wire incorporating insulators to provide an electrical break between different supply phases or a change of system voltage. Drivers of electric trains should reduce power when approaching a neutral section and must not stop in a neutral section, except in an emergency. In 1987, experimental signs to mark the approach to, and site of, a neutral section were erected at four sites between Grantham and Bawtry, south of Doncaster. Both signs bear the same symbol against a black or white background, respectively [18.19 & 18.20]. They were adopted as standard in 1988.

[18.19] Neutral Section Warning Board. Click Here for Photo
Area: All Areas   Usage: High   Status: Current
[18.20] Neutral Section Indication Board.
Area: All Areas   Usage: High   Status: Current

The lines in the Channel Tunnel, which opened in May 1994, are electrified on the 25 kV AC overhead wire system. Since the existing railways near the UK portal of the Channel Tunnel were electrified on the 750 V DC third rail system, drivers of all trains running between the two systems were required to carry out a traction current changeover procedure. Signs marked the point where the 25 kV overhead wires end, these comprising a circular black board with "25000" in white and a red diagonal cross [18.21].

[18.21] End of Eurotunnel Catenary Supply.
Area: Cheriton   Usage: Low   Status: Uncertain