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Following a derailment on the curve at Morpeth on 7 May 1969, the British Railways Board agreed to the provision of advance warning indicators (AWIs) on approach to certain speed restrictions. The new indicators, which first appeared in 1971 and became known as 'Morpeth boards', had yellow figures within a yellow border on a circular black background [13.24]. They were placed at braking distance in rear of the start of the speed restriction and in many cases were floodlit at night. An advance warning indicator applicable to a speed restriction on a diverging route carried an additional directional arrow below [13.25]. In some places, a vertical arrow was exhibited below an advance warning indicator that applied to a speed restriction on the straight route beyond a diverging junction [13.26].
In August 1971, a speed restriction of 25 mph was experimentally imposed on Class 7, 8 and 9 freight trains over the lines between Hartford CLC Junction and Dee Marsh North Junction and between Dee Marsh Junction and Bidston Dee Junction, on the London Midland Region. Where a higher speed applied to other classes of trains, this was indicated by the bottom figure of a differential 'cut-out' speed restriction sign erected at the point of commencement [13.27]. Over the following months, similar signs were installed on a few other low-speed lines on the London Midland Region. |
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In February 1977, a 'cut-out' style speed restriction sign (see [13.17]) indicating a permissible speed of 125 mph on the Up Main line at Reading (Western Region) was replaced by an experimental indicator showing the figures "125" in reflective yellow on a black background [13.28]. |
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Where a change of permissible speed occurs within a tunnel, the speed may be indicated by a permanently illuminated indicator [13.29]. These indicators are installed in the central Liverpool area, on the Northern City Line (between Moorgate and Finsbury Park) and on the lines approaching London King's Cross station. |
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The Class 253 and 254 'High Speed Trains' (or 'InterCity 125s') were introduced to British Rail in 1976. Because of their superior braking performance, they were permitted to travel over specified sections of track at a higher speed than other trains. On the Western Region, a yellow triangle was placed on the posts of speed restriction signs, below the cut-out figures, to denote those places where a variation in the permissible speed for certain classes of trains applied. The triangle pointed up if the variation was higher [13.30] or down if it was lower [13.31]. Neither the permitted speed nor the application of the variation was stated, the details of which were to be found in the relevant Sectional Appendix. The first of these signs were installed in May 1977, marking the start of sections where a different permissible speed applied to HSTs.
[13.30] Differential Permanent Speed Restriction Sign.
Area: Western Region Usage: Low Status: Historical |
[13.31] Differential Permanent Speed Restriction Sign.
Area: Western Region Usage: Low Status: Historical |
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Boards were installed in October 1977 to denote sections of the East Coast Main Line where HSTs were permitted to run at 125 mph during daylight hours. The commencement boards at the start of each section were circular with a letter "A" [13.32], and the termination boards were square with a letter "B" [13.33]. These boards were installed as a temporary measure, at various sites between Peterborough and Darlington.
[13.32] HST Commencement Board.
Area: Peterborough - Darlington Usage: Low Status: Historical |
[13.33] HST Termination Board.
Area: Peterborough - Darlington Usage: Low Status: Historical |
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Where an advance warning indicator was required on the approach to a permanent speed restriction applicable only to HSTs, it bore the letters "HST" above the speed figure [13.34]. |
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In 1979, experimental reflectorised permanent speed restriction signs were erected at Metropolitan Junction and Gillingham (Kent). Each sign had black figures on a circular yellow background, surrounded by a black border [13.35] and was therefore of similar appearance to an advance warning indicator (see [13.24]) with the colours reversed. |
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Differential speed restrictions were already being applied in connection with temporary speed restrictions (see Section 14) and at some level crossings (see Section 16) when, c.1980, their use was extended to certain permanent speed restrictions. Where differential speeds apply, the permanent speed restriction sign displays two speeds, one above the other (see [13.27]). Where an advance warning indicator is provided in relation to a differential speed restriction, it will also show two speeds [13.36]. This form of differential speed restriction has come to be referred to as a 'standard differential' PSR, as distinct from a 'non-standard differential' PSR which specifies the relevant type of train by letters, e.g. "HST". |
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Signs showing higher permissible speeds applicable only to HSTs were installed on the Scottish Region from June 1981 on the East Coast Main Line and the Edinburgh to Aberdeen line. The commencement sign was a yellow square showing the applicable speed below the letters "HST" [13.37], and the termination sign was a yellow diagonal board with a letter "T" instead of a speed [13.38]. Some of these signs were co-located with ordinary speed signs, and others were installed in isolation. Drivers of HSTs that passed a commencement sign could disregard any ordinary speed restriction signs indicating a lower speed, including any further signs beyond, but ordinary signs indicating a higher speed continued to apply. The higher speeds applied until reaching a termination sign. Signs installed at either end of the Forth Bridge in January 1982 had two sets of letters, referring to HSTs and DMUs [13.39 & 13.40]. Commencement and termination signs bearing the letters "MU" instead of "HST" were subsequently provided on some other Scottish Region routes to indicate higher permissible speeds applicable only to Class 15x series diesel multiple unit trains.
Pentagonal signs coloured yellow were installed between Dearne Junction and Moorthorpe (Eastern Region) in October 1984 to mark the commencement and termination of higher permissible speeds for HSTs. The commencement sign was an upward-pointing pentagon indicating the higher speed at which HSTs may travel [13.41]. This higher speed applied until a termination sign was reached, this being a downward-pointing pentagon indicating the lower speed to which HSTs must revert [13.42].
[13.41] Commencement Sign.
Area: Dearne Junction - Moorthorpe Usage: Low Status: Historical |
[13.42] Termination Sign.
Area: Dearne Junction - Moorthorpe Usage: Low Status: Historical |
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