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Section 12: Signs associated with Train Protection Systems

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In preparation for the opening of the first section of the Channel Tunnel Rail Link (CTRL) in 2003, ordinary 'AWS gap' signs (see [12.4 & 12.5]) were provided at places where lines signalled with lineside signals abut lines with cab signalling (Fawkham Junction, Ashford and Dollands Moor). These replaced the previous signs at Dollands Moor (see [12.11 & 12.12]). At the same time, warning signs were installed approaching the areas of commencement of cab signalling, with the word "cab" on a white background [12.18]. This sign is placed some distance before the sign that marks the actual commencement of cab signalling (see [12.13]). A revised style of sign denoted the end of cab signalling, with the word "cab" on a white background and a red cross superimposed [12.19].

[12.18] Warning of Commencement of Cab Signalling.
Area: Various   Usage: Medium   Status: Current
[12.19] End of Cab Signalling.
Area: Various   Usage: Medium   Status: Current

The national programme of Train Protection & Warning System (TPWS) fitment reached the lines worked by the Radio Electronic Token Block (RETB) system in 2003. RETB is a low-cost signalling system that replaces working stop signals with stop boards, some of which require TPWS fitment. Because signalmen receive no indication of TPWS failures in an RETB area, a 'Lineside Status Indicator' (LSI) comprising a blue light is installed at each TPWS-fitted stop board to inform drivers whether the TPWS equipment is operating correctly. A steady blue light in the LSI [12.20] means that the TPWS is in its normal state, energised and providing over-run protection. The blue light will flash [12.21] when the TPWS equipment is de-energised, which occurs when a correct token is issued (and any ground frame or plunger is operated). If the light in the LSI is out, the driver must report it to the signalman as a fault. This equipment was initially commissioned at Tywyn on the Cambrian Line.

[12.20] TPWS Indicator (steady).
Area: Tywyn   Usage: Low   Status: Historical
[12.21] TPWS Indicator (flashing).
Area: Tywyn   Usage: Low   Status: Historical

A few weeks after they were brought into use, the backboards of the LSIs at Tywyn were changed to black. The black backboard became the standard for future installations of LSIs [12.22 & 12.23].

[12.22] TPWS Indicator (steady).
Area: Various   Usage: High   Status: Current
[12.23] TPWS Indicator (flashing).
Area: Various   Usage: High   Status: Current

If a stop board fitted with a TPWS indicator can be approached at speed, a repeater may be necessary. This particularly applies at a TPWS fitted stop board at an intermediate token exchange point where there is no crossing loop. Where a repeater TPWS indicator is provided, it repeats the indication at the stop board and is mounted below the distant board on the approach to it [12.24 & 12.25]. The first repeater LSI was put on trial for two days in September 2003, fitted to the Up distant board at Evanton. It was fully commissioned in October 2003 and was soon followed by others.

[12.24] TPWS Repeater Indicator (steady). Click Here for Photo
Area: Various   Usage: Low   Status: Current
[12.25] TPWS Repeater Indicator (flashing).
Area: Various   Usage: Low   Status: Current

A TPWS repeater indicator may be required if the stop board is not visible from the position where trains normally stop. One of these was provided at Oban in October 2003 [12.26 & 12.27].

[12.26] TPWS Repeater Indicator (steady). Click Here for Photo
Area: Various   Usage: Low   Status: Current
[12.27] TPWS Repeater Indicator (flashing).
Area: Various   Usage: Low   Status: Current

Around 2006, Arriva Trains Wales trialled AWS reminder boards with an inverted triangular shape [12.28] at certain stations on the Welsh Valley Lines. The signs were installed at the platform ends. Similar signs have subsequently been provided at various other stations, both on and off the Arriva Trains Wales network.

[12.28] AWS Reminder Board. Click Here for Photo
Area: Various   Usage: Medium   Status: Current

The opening of Section 2 of the Channel Tunnel Rail Link in 2007 saw a return to the provision of AWS boundary signs with black backgrounds (see [12.11 & 12.12]), although the new 'end of AWS' signs have a single diagonal red stripe [12.29]. Note that the letters "AWS" on these signs may refer to the French KVB system rather than the BR AWS system. "KVB" stands for 'Contrôle de Vitesse par Balises', meaning 'Speed Control by Beacons'. KVB is in use on the CTRL approach to St. Pancras International station.

[12.29] End of AWS.
Area: Various   Usage: Medium   Status: Current

From 2009, the train-operated (hydro-pneumatic) points on lines worked by the No-Signalman Token Remote (NSTR) system were being converted to conventional power operation. As this work was carried out, TPWS indicators (see [12.22 & 12.23]) were provided at the stop boards applicable to trains departing a crossing loop in the usual direction. These are in addition to the TPWS indications located inside the token instrument huts.


The stop board protecting the link to the North Norfolk Railway at Sheringham station was provided with a TPWS lineside status indicator in 2011. The black backboard is labelled with the letters "TPWS" to the right of the blue light [12.30]. Since the TPWS Train Stop System (TSS) loops at the stop board are permanently energised, this indicator is not equipped to show a flashing indication.

[12.30] TPWS Indicator.
Area: Sheringham   Usage: Low   Status: Uncertain

In 2013, experimental signs were installed at certain locations on the London, Tilbury & Southend line to denote the presence of TPWS Overspeed System (OSS) loops. A sign associated with a signal OSS has a red border [12.31] and a sign associated with a permanent speed restriction (P.S.R.) OSS has a yellow border [12.32]. The boards were manufactured with the set speed (the speed below which the train must pass to avoid a TPWS intervention) displayed in the centre but this information has been covered over.

[12.31] TPWS Sign (associated with a signal).
Area: LT&S line   Usage: Low   Status: On Trial
[12.32] TPWS Sign (associated with a P.S.R.).
Area: LT&S line   Usage: Low   Status: On Trial