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Section 12: Signs for Train Protection Systems and Cab Signalling

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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 [12.12 & 12.13]). At the same time, warning signs were installed approaching the areas of commencement of cab signalling, with the word "cab" on a white background [12.20]. This sign is placed some distance before the sign that marks the actual commencement of cab signalling (see [12.14]). A revised style of sign denoted the end of cab signalling, with the word "cab" on a white background and a red cross superimposed [12.21].

[12.20] Warning of Commencement of Cab Signalling.
Area: Various   Usage: Medium   Status: Current
[12.21] End of Cab Signalling. Click Here for Photo
Area: Various   Usage: Medium   Status: Current

The first section of the CTRL opened in September 2003, between Fawkham Junction and the Channel Tunnel. This was Britain's first high-speed line. The opening of the second section in November 2007 completed the route, which now runs between London St. Pancras and the Channel Tunnel. High-speed lines do not have lineside signals, because a driver could not reasonably be expected to read and interpret a signal aspect at high speed. Instead, cab signalling is used, with fixed markers placed at the lineside to mark the start of each block section. The CTRL is signalled with a cab signalling system called TVM. This is the same system as used in the Channel Tunnel itself, as well as on the high-speed lines in France, where high-speed lines had been in operation for many years beforehand. The letters "TVM" stand for 'Transmission Voie-Machine', which means 'Track to Train Transmission'. The British block markers are based on the French 'repères', bearing a solid yellow triangle on a blue square background [12.22]. The apex of the triangle points towards the line to which it applies. The marker indicates to the driver the position at which the train must come to a stand when a 'stop' indication is shown on the cab signalling display.

A shunt marker is provided to identify the origin of a shunting movement at places where no block marker is provided. A shunt marker is a five-sided shape and has a white chevron on a violet background [12.23]. The tip of the chevron points towards the line to which it applies. Every shunt marker on the CTRL is provided with an auxiliary signal (see [9.60]), which is illuminated when the shunt marker is 'opened'. On the French high-speed lines, the equivalent of the shunt marker is the 'jalon de manœuvre', similarly coloured but different in shape.

[12.22] TVM Block Marker / CBTC Block Marker (e.g. applies to the line on the right). Click Here for Photo
Area: CTRL / Crossrail   Usage: High   Status: Current
[12.23] TVM Shunt Marker / ETCS Shunt Entry Board (e.g. applies to the line on the right). Click Here for Photo
Area: CTRL / Cambrian Lines   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 [12.24] means that the TPWS is in its normal state, energised and providing overrun protection. The blue light will flash [12.25] 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, in June 2003.

[12.24] TPWS Indicator (steady).
Area: Tywyn   Usage: Low   Status: Historical
[12.25] 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 [12.26 & 12.27].

[12.26] TPWS Indicator (steady).
Area: Various   Usage: High   Status: Current
[12.27] 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 [12.28 & 12.29]. 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.

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

A TPWS repeater indicator may also be provided on the approach to a TPWS-fitted stop board with restricted sighting, in which case it can be independently mounted [12.30 & 12.31]. One of these was provided at Oban in October 2003.

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

Around 2006, Arriva Trains Wales trialled AWS reminder boards with an inverted triangular shape [12.32] 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.

[12.32] 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 November 2007 saw a return to the provision of AWS boundary signs with black backgrounds (see [12.12 & 12.13]), although the new 'end of AWS' signs have a single diagonal red stripe [12.33]. 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 was installed on the CTRL approach to St. Pancras International station in 2007 and was later added in the Ashford International station area in 2018.

[12.33] 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 [12.26 & 12.27]) 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 European Train Control System (ETCS) is a signalling and train control system developed with the backing of the European Union. ETCS may be overlaid onto ordinary lineside signalling, or alternatively it may function solely as cab signalling. The standard form of block marker for ETCS lines with cab signalling is similar to a TVM block marker (see [12.22]), but the triangle is replaced by an arrow [12.34]. The arrow points towards the line to which the marker applies. In the unusual situation where a block marker is mounted directly over the line to which it applies, the arrow points down [12.35]. The first British application of ETCS cab signalling was on the Cambrian Lines in 2010/2011.

Shunt entry boards associated with ETCS cab signalling are of similar appearance and purpose to the TVM shunt markers on the Channel Tunnel Rail Link (see [12.23]), but auxiliary signals are not provided.

[12.34] ETCS Block Marker (e.g. applies to the line on the right). Click Here for Photo
Area: All Areas   Usage: High   Status: Current
[12.35] ETCS Block Marker applicable to the line below.
Area: All Areas   Usage: Low   Status: Current

The stop board protecting the link to the North Norfolk Railway at Sheringham station was provided with a TPWS lineside status indicator in March 2011. The black backboard is labelled with the letters "TPWS" to the right of the blue light [12.36]. 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.

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

In June 2013, experimental signs were installed at certain locations on the London, Tilbury & Southend line to denote the presence of TPWS Overspeed System (OSS) loops. Each sign comprises a white inverted triangle with the letters "TPWS" in black. A sign associated with a signal OSS has a red border [12.37], and a sign associated with a permanent speed restriction (PSR) OSS has a yellow border [12.38]. The boards were manufactured with the applicable set speed (the speed below which a train must pass to avoid a TPWS intervention) displayed in the centre, but this information was initially covered over. The set speeds on the signs associated with PSR OSSs were subsequently uncovered [12.39], and a number of similar installations were made at various locations around the Anglia Route. Informing drivers of the set speed prompts them to check their speed and enables them to decelerate slightly if necessary, to avoid an unexpected TPWS intervention.

[12.37] TPWS Sign associated with a Signal OSS.
Area: LT&S line   Usage: Low   Status: On Trial
[12.38] TPWS Sign associated with a PSR OSS.
Area: LT&S line   Usage: Low   Status: Historical
[12.39] TPWS Sign associated with a PSR OSS, showing the set speed (e.g. 69 mph).
Area: Anglia Route   Usage: Low   Status: On Trial

The Crossrail Central Operating Section, which opened in March 2021, has a form of cab signalling called Communications-Based Train Control (CBTC). The block markers for CBTC have the same appearance as those used for TVM cab signalling (see [12.22]). Signs denoting the start and end of CBTC cab signalling are similar to the standard signs for start and end of cab signalling (see [12.14] and [12.21]), but the word "cab" is replaced by the letters "CBTC" [12.40 & 12.41]. The system of cab signalling is specified on these signs to take account of trains transitioning to and from areas with ETCS cab signalling.

[12.40] Start of CBTC Cab Signalling.
Area: NR/Crossrail Interfaces   Usage: Low   Status: Current
[12.41] End of CBTC Cab Signalling. Click Here for Photo
Area: NR/Crossrail Interfaces   Usage: Low   Status: Current