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Section 29: Signs for Engineering Trains or Test Trains

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The signs described in this section are applicable only to specific types of engineering trains or to trains undergoing tests. They are disregarded by drivers of ordinary trains.


The Advanced Passenger Train (APT) was a tilting train introduced by British Rail in 1979 for use on West Coast Main Line services. Its tilt system enabled it to travel at higher speeds than conventional trains over curved sections of track. Ultimately, these higher speeds would be continuously indicated to APT drivers on a cab display by a system called C-APT (Control APT). For the duration of the tests which commenced in 1979, however, special lineside marker boards were affixed to electrification structures, between Carnforth (London Midland Region) and Glasgow Central (Scottish Region) via Beattock. The sign at the commencement of the special permissible speed was a square board with a white background [29.1], while the sign at the braking point where the permissible speed was reduced was a diagonal board with a yellow background [29.2].

[29.1] Commencement of indicated permissible speed for prototype APT.
Area: Carnforth - Glasgow Central   Usage: Low   Status: Historical
[29.2] Braking point for indicated lower permissible speed ahead for prototype APT.
Area: Carnforth - Glasgow Central   Usage: Low   Status: Historical

In 1981, in connection with the electrification of the Great Northern Line, indicator boards for the use of technical departments were positioned alongside the lines from London King's Cross to Welwyn Garden City and Hertford North (Eastern Region). The boards were diamond shaped and contained either a number "1" or "2" [29.3].

[29.3] Indicator Board.
Area: Great Northern Line   Usage: Low   Status: Historical

Further lineside marker boards were provided in 1981 between Beattock and Carstairs (Scottish Region) in connection with testing of the APT, displaying a figure on either a white triangle [29.4] or a yellow square [29.5]. The APT was withdrawn from passenger service in 1985.

[29.4] APT Test Marker.
Area: Beattock - Carstairs   Usage: Low   Status: Historical
[29.5] APT Test Marker.
Area: Beattock - Carstairs   Usage: Low   Status: Historical

'Sandite' is a substance that can be applied to the rail head by a special train at locations prone to poor adhesion. Lineside markers were installed to assist the staff on board the Sandite train in locating the sites concerned. The first sign, an upright yellow rectangle with three black diagonal bars [29.6], gives advance warning of a Sandite application site. This marker is followed by a similar yellow board with two bars [29.7] at the point where application should begin and finally a board with just one bar [29.8] at the point where application should end.

[29.6] Advance warning of Sandite application site.
Area: All Areas except Scottish Region   Usage: High   Status: Current
[29.7] Commencement of Sandite application site.
Area: All Areas except Scottish Region   Usage: High   Status: Current
[29.8] Termination of Sandite application site.
Area: All Areas except Scottish Region   Usage: High   Status: Current

Although it is not a standard sign, a yellow marker with a letter "P" [29.9] is provided at some locations to denote that the application of Sandite is prohibited.

[29.9] Sandite Prohibition Marker.
Area: Salisbury - Exeter   Usage: Low   Status: Uncertain

In 1989, lineside markers were installed at certain locations on the Scottish Region, applicable to Civil Engineer's staff on board the Ultrasonic Test Train, which detects rail defects. The signs, which comprise an upright blue rectangle with a diagonal yellow stripe [29.10], are installed at geographical junction locations, adjacent to the facing points, and act as a designated datum point.

[29.10] Ultrasonic Test Train Marker. Click Here for Photo
Area: Scottish Region   Usage: Medium   Status: Uncertain

From 1992, lineside marker boards were installed at Sandite application sites on the Scottish Region. The standard Sandite marker boards (see [29.6 - 29.8]) are not used in Scotland, where alternative white octagonal boards are provided instead. The board marking the commencement of the portion of line over which Sandite requires to be applied bears the abbreviation "sand" [29.11], while the board at the finish point is similar but has a diagonal red stripe superimposed [29.12]. No advance warning boards are provided in conjunction with these signs.

[29.11] Commencement of Sandite application site.
Area: Scottish Region   Usage: Medium   Status: Current
[29.12] Termination of Sandite application site.
Area: Scottish Region   Usage: Medium   Status: Current

In 1998, small blue markers [29.13] were installed on the approaches to Theale, Midgham and Thatcham stations (Great Western Zone). These markers were for guidance during braking tests on Class 165/166 ('Turbo') trains.

[29.13] Turbo Braking Trials Marker.
Area: Reading - Newbury   Usage: Low   Status: Obsolescent

A company called 'LaserThor' developed a system for removing rail head contamination using lasers. A number of trials were conducted, latterly with the laser equipment being mounted on a Multi Purpose Vehicle (MPV). In the autumn of 2003, trials took place at Oxshott and Wanborough on the Southern Region. Signs were installed at each test site to assist the MPV operator. A sign reading "laser on" [29.14] marked the start of the test site. This was followed by signs lettered "A", "B" and "C" [29.15] at intervals of a quarter mile. The last board in the series, worded "laser off" [29.16], was located one mile from the start of the test site.

[29.14] "Laser On" Sign.
Area: Oxshott / Wanborough   Usage: Low   Status: Historical
[29.15] Intermediate Signs.
Area: Oxshott / Wanborough   Usage: Low   Status: Historical
[29.16] "Laser Off" Sign.
Area: Oxshott / Wanborough   Usage: Low   Status: Historical

Leaf residue on the rail head can be removed by high-pressure water jetting. On the Scotland Territory, octagonal boards were installed from 2006 at the commencement and termination points of locations where water jetting is carried out. The board marking the commencement point bears the words "water jet" [29.17], while the board at the termination point is similar but has a diagonal red stripe superimposed [29.18].

[29.17] Commencement of Water Jetting site. Click Here for Photo
Area: Scotland Territory   Usage: Low   Status: Current
[29.18] Termination of Water Jetting site.
Area: Scotland Territory   Usage: Low   Status: Current

During the autumn of 2006, marker boards lettered "A", "B" and "C" [29.19 - 29.21] were provided between Ockley and Warnham (Southern Territory) for autumn measurement testing. These signs concerned both the notified MPV treatment train and the Southern test train but with different meanings applying to each. To the treatment train, the "A" marker board [29.19] indicated the point where the notified test specific treatment should be applied. The "B" marker board [29.20] was disregarded by the treatment train and when the "C" marker board [29.21] was reached, it returned to its usual treatment diagram. For the test train, the "A" marker board [29.19] meant "prepare to conduct brake test". A full service brake application had to be made when the "B" marker board [29.20] was reached. The "C" marker board [29.21] did not apply to the test train.

[29.19] "A" Marker Board.
Area: Ockley - Warnham   Usage: Low   Status: Historical
[29.20] "B" Marker Board.
Area: Ockley - Warnham   Usage: Low   Status: Historical
[29.21] "C" Marker Board.
Area: Ockley - Warnham   Usage: Low   Status: Historical

The High Output train (Track Renewal System) is a mechanised system for carrying out plain line track renewals. Ordinarily, the train would be stopped at the preceding controlled signal before moving forward to the work site. As part of a trial undertaken on the London North Eastern and East Midlands Routes in 2014 aimed at maximising the production time during a single shift, the train will stop at the actual site of work before a possession is taken around it. This is known as the "Flexible Train Arrival Point" (FTAP) and its position is denoted by a temporary marker at the lineside [29.22]. A series of countdown markers [29.23] is erected on the approach to the stopping point.

[29.22] FTAP Stopping Point Marker.
Area: LNE and EM Routes   Usage: Medium   Status: On Trial
[29.23] FTAP Countdown Markers ( (a) - Outer board; (b) - Intermediate board; (c) - Inner board ).
Area: LNE and EM Routes   Usage: Medium   Status: On Trial