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Section 13: Permanent Speed Restriction Signs

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Early in 1986, an experimental reflectorised type of 'preliminary speed board' was put on trial at two sites on the Edinburgh - Glasgow line. The board was shaped like an inverted triangle [13.38]. This was intended as a replacement for the earlier floodlit warning boards (see [13.20]).

[13.38] Experimental Preliminary Speed Board.

The new design of reflectorised advance warning indicator introduced as standard later in 1986 was similar in shape to the trial version, but had a white background and a yellow border [13.39]. The usual shape of the sign is modified to a five-sided variant where there is limited clearance or where a wider or taller than usual board is needed to accommodate the lettering [13.40].

[13.39] Advance Warning Indicator.	[13.40] Advance Warning Indicator (alternative shape).

The Scottish Region style of reflectorised P.S.R. indicator (see [13.33]) was adopted as the standard throughout B.R. in c.1987. However, in contrast to the Scottish Region practice, a directional arrow sign, where provided, would be positioned above the speed board [13.41 & 13.42]. Exceptionally, a directional arrow may point upwards [13.43], indicating that the sign applies to the straight route.

[13.41] Permanent Speed Restriction Sign with Directional Arrow (e.g. applicable to right-hand divergence).	[13.42] Permanent Speed Restriction Sign with Directional Arrows applicable to divergences in both directions.	[13.43] Permanent Speed Restriction Sign with Directional Arrows applicable to straight route as well as diverging route.

An advance warning indicator (A.W.I.) applicable to a speed restriction on a diverging route is fitted with a directional arrow pointing in the appropriate direction. The positioning of the arrow sign relative to the speed indicator followed the practice for standard circular P.S.R. signs (see [13.35] and [13.41]), i.e. the arrow was placed above [13.44], except on the Scottish Region, where it would be placed below [13.45]. Two arrows are displayed if the A.W.I. applies to restrictions of equal speed on diverging routes to the left and the right [13.46].

[13.44] Advance Warning Indicator with Directional Arrow (e.g. applicable to left-hand diverging route).	[13.45] Advance Warning Indicator with Directional Arrow (e.g. applicable to right-hand diverging route) (Scottish Region).	[13.46] Advance Warning Indicator with Directional Arrows applicable to diverging routes in both directions.

A new design of standard differential speed restriction sign was introduced in which both speeds are exhibited on a single board and separated by a horizontal bar [13.47]. In areas of limited clearance, an elliptical sign is used [13.48]. A corresponding form of differential advance warning indicator was also introduced [13.49].

[13.47] Standard Differential Permanent Speed Restriction Sign.	[13.48] Standard Differential Permanent Speed Restriction Sign for use in areas of limited clearance.	[13.49] Advance Warning Indicator applicable to a standard differential permanent speed restriction.

Permanent speed restriction signs concerning only specific types of trains were introduced throughout B.R. from c.1987. Unlike the earlier signs applicable only to HSTs (see [13.22 & 13.24]), these signs do not override any subsequent signs indicating a lower speed. There is therefore no equivalent to the termination sign (see [13.23 & 13.25]). The signs, placed at the start of each differential speed restriction, are based on the standard circular speed sign with the addition of identifying letters [13.50]. An elliptical sign is available for areas of limited clearance or for when the speed is composed of three figures, e.g. "100" [13.51].

The types of trains to which the signs may apply are identified by the codes below:

"HST" = High Speed Trains (i.e. Class 253 & 254, and subsequently also to Class 91 locomotives with Mark 4 coaches and to certain classes of multiple unit trains)
"MU" = Multiple Unit Trains
"DMU" = Diesel Multiple Unit Trains
"EMU" = Electric Multiple Unit Trains
"SP" = 'Sprinters' (applies only to certain classes of DMUs)
"WES" = Class 442 ('Wessex Electric') EMUs
"LUL" = London Underground Limited Trains; also applies to other EMUs fitted with trip cock apparatus
"CS" = Class 67 Locomotives

Restrictions of this type are referred to as 'non-standard differential' P.S.R.s. Generally where these signs are installed, a higher speed applies to the specified type of train indicated, except that a lower speed may apply where "LUL" or "CS" is shown [13.52]. Exceptionally, more than one code may be displayed on the sign [13.53].

[13.50] Non-standard Differential Permanent Speed Restriction Sign.	[13.51] Non-standard Differential Permanent Speed Restriction Sign.


[13.52] Non-standard Differential Permanent Speed Restriction Sign (e.g. lower speed applicable to LUL trains).	[13.53] Non-standard Differential Permanent Speed Restriction Sign.

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