Section 8: Over-run Prevention and Mitigation

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In some instances it has been felt necessary to put in place extra measures to guard against the possibility of an over-run (i.e. prevention), or to lessen the outcome of an over-run where one has taken place (i.e. mitigation). An over-run can take place at a station stop, or rather more seriously, past a signal that is showing a 'danger' indication. The latter occurrence has come to be termed a 'SPAD' - Signal Passed At Danger.

In complex layouts, line identifiers are sometimes fitted to signals (usually where they are gantry-mounted), where there are several adjacent lines and signals [8.1]. This helps drivers to pick out the signal that applies to their train.

[8.1] Line Identifier.

To enable drivers to locate their position, the Southern Railway had a practice of installing yellow (or amber) location lights [8.2] on the approach to passenger halts where no signals existed. These lights were commonly provided upon closure of a signal box, and removal of signals from the vicinity of a passenger station. In rare cases, the light was only displayed for trains booked to stop at the halt during darkness.

[8.2] Location Light (Southern Railway).

In December 1928, a fog location lamp was provided 50 yards on the approach to a signal at Borough Market Junction (Southern Railway). The lamp had a letter "F" on the face [8.3], and was only switched on during foggy weather. It was short-lived, being removed in April 1929.

[8.3] Fog Location Lamp (Borough Market Junction, Southern Railway).

In 1928, a location board was provided 50 yards on the approach to signals at Vauxhall on the Southern Railway [8.4], to enable drivers to locate their position during foggy weather. This was replaced by a larger striped board in 1929 [8.5].

[8.4] Fog Location Board (Vauxhall, Southern Railway).	[8.5] Fog Location Board (Vauxhall, Southern Railway).

When King's Cross (LNER) was resignalled in 1932, part of the layout was referred to as "A" route to "E" route. Identification letters, illuminated at night, were fitted to either side of the signal gantry directly above the lines to which they referred [8.6]. The corresponding letters also appeared on permanent speed restriction signs applying over those routes (see [13.11]).

[8.6] Identification Letter (e.g. route "A") (King's Cross, LNER).

In 1933, the Southern Railway provided experimental fog location boards or posts at Earlswood and Haywards Heath. At Earlswood, a large square board with vertical stripes [8.7] was installed on the skew to the track, 100 yards on the approach to a signal. White posts [8.8] were installed 100 yards on the approach to two signals at Haywards Heath. The fog location board and posts at both places were removed in 1934.

[8.7] Experimental Fog Location Board (Earlswood, Southern Railway).	[8.8] Experimental Fog Location Post (Haywards Heath, Southern Railway).

In 1943, an indicator plate was provided on the approach to Rogate station (Southern Railway) [8.9], to allow drivers to locate their position.

[8.9] Location Indicator (Rogate, Southern Railway).

As early as 1956, trials took place with the provision of countdown markers on the approach to a distant signal at Newark (Eastern Region).

In the 1960s, marker lights were fixed to the wall of Glasgow Queen Street High Level Tunnel (Scottish Region) to assist drivers in locating a signal in the tunnel in conditions of poor visibility. There is a steep downhill gradient on the approach to the signal concerned. The marker lights comprised groups of continuously lit white lights (three at 108 yards, two at 62 yards, and one at 19 yards from the signal).

In the early 1960s, the Southern Region carried out experiments with countdown markers on the approach to signals between Esher and West Byfleet. These had horizontal black stripes on a white background. Their provision was connected with the lack of AWS on the Southern Region.

In 1975, countdown markers were installed in Chipping Sodbury Tunnel (Western Region) on the approach to a signal.

On the Scottish Region, signal M183 at Uddingston had been passed at 'danger' on numerous occasions. Although the sighting was good, drivers of light engines in particular had been misjudging their braking on the downhill approach to the signal. The problem was addressed in 1987 by the provision of experimental countdown markers on the approach to the signal [8.10]. The markers were installed at 436 yards, 294 yards and 160 yards in rear of the signal. This style of countdown marker was subsequently adopted nationally as one means of reducing SPAD occurrences at signals that have a history of SPAD incidents or that are considered to be 'high risk'. As standard, the markers are installed at 300 metres, 200 metres and 100 metres from the signal.

[8.10] Countdown Markers ( (a) - Outer board; (b) - Intermediate board; (c) - Inner board ).

In 1988, experimental countdown markers were installed on the approach to two signals at Preston (London Midland Region). These signs had black diagonal stripes on a white background [8.11].

[8.11] Countdown Markers ( (a) - Outer board; (b) - Intermediate board; (c) - Inner board ) (Preston, LMR).

In 1990, notice boards were placed on each rail approach to Irvine station (Scottish Region), for the purpose of preventing station over-runs [8.12].

[8.12] 'Station Ahead' Board (Irvine, Scottish Region).

Five experimental boards [8.13] were installed between Chichester and Warblington (Southern Region) when the line was resignalled in 1992. Each board was installed at generally 650 yards on the approach to a stop signal, and all but one were accompanied by an AWS warning indication. These boards were intended to assist drivers in locating the signals concerned. They were removed in 1999.

[8.13] Signal Reminder Board (Southern Region).

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