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Section 1: Early Signals

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In January 1841, managers of the various railway companies met in Birmingham to discuss the standardisation of safety matters. It was recommended that the Liverpool & Manchester Railway's signal colours (red for 'danger', green for 'caution', white for 'clear') be adopted as standard. Later that year, those colours were used as the light indications shown by the first railway semaphore signal (see [2.1 - 2.3]).

To show the 'caution' indication, the 'flag signal' was introduced on the Great Western Railway from February 1841. Also known as a 'kite', it consisted of a pair of coloured curtains inside a triangular frame. The flag signal was usually used in conjunction with a disc and crossbar signal and positioned at a lower height. When the red flag was unfurled [1.28], this indicated 'danger'. The green flag meant 'caution' [1.29].

[1.28] Flag Signal showing 'Danger'.
Area: GWR   Usage: Unknown   Status: Historical
[1.29] Flag Signal showing 'Caution'.
Area: GWR   Usage: Unknown   Status: Historical

The flag signals were prone to being torn to ribbons every few days by the wind. To replace them, Brunel introduced the 'caution board' or 'fantail' in January 1842. This comprised an arrow shaped board painted red on one side and green on the other. When the board pointed towards the track and the red side was visible to approaching trains [1.30], the meaning was 'danger'. When the board pointed away from the track with its green side visible [1.31], it indicated 'caution'. After the 'caution' time interval had expired, the caution board was turned edge on to the track so as to be practically invisible.

[1.30] Caution Board showing 'Danger'.
Area: GWR   Usage: Unknown   Status: Historical
[1.31] Caution Board showing 'Caution'.
Area: GWR   Usage: Unknown   Status: Historical

Early in 1842, the discs and crossbars on the disc and crossbar signals (see [1.24 - 1.27]) were repainted red to improve their visibility [1.32 - 1.35]. The shape of the signal alone would determine its indication by day.

[1.32] Disc and Crossbar Signal showing 'Danger'.
Area: GWR   Usage: Unknown   Status: Historical
[1.33] Disc and Crossbar Signal showing 'Clear'.
Area: GWR   Usage: Unknown   Status: Historical
[1.34] Double Disc and Crossbar Signal showing 'Danger'.
Area: GWR   Usage: Unknown   Status: Historical
[1.35] Double Disc and Crossbar Signal showing 'Clear'.
Area: GWR   Usage: Unknown   Status: Historical

In addition to the usual red vanes for 'danger' (see [1.5]), signals on the Edinburgh & Glasgow Railway had a single green vane for 'caution' [1.36] and a white vane for 'clear' [1.37].

[1.36] Vane Signal showing 'Caution'.
Area: Edinburgh & Glasgow Railway   Usage: Unknown   Status: Historical
[1.37] Vane Signal showing 'Clear'.
Area: Edinburgh & Glasgow Railway   Usage: Unknown   Status: Historical

A board signal could indicate 'caution' by being painted green on one side [1.38]. A green light was shown at night.

[1.38] Board Signal showing 'Caution'.
Area: Various   Usage: Unknown   Status: Historical

The Caledonian Railway used a board signal with a tab protruding from one edge. One side of the board was painted red for indicating 'danger' [1.39] and the other side was green for 'caution' [1.40]. The tab was an aid to determining the aspect shown by the signal on occasions when lighting conditions made colour recognition difficult. Drivers knew that the tab being on the right-hand side, nearest the track, meant the signal was displaying 'danger'. To indicate 'clear', the board was turned edge on and a white light was shown at night (see [1.2]).

[1.39] Board Signal showing 'Danger'.
Area: Cal.R   Usage: Unknown   Status: Historical
[1.40] Board Signal showing 'Caution'.
Area: Cal.R   Usage: Unknown   Status: Historical

As an alternative to the tab, signals on the Central Division of the Caledonian Railway had one edge shaped like an arrow [1.41 & 1.42], similar to the GWR's 'fantail' signal (see [1.30 & 1.31]).

[1.41] Board Signal showing 'Danger'.
Area: Cal.R   Usage: Unknown   Status: Historical
[1.42] Board Signal showing 'Caution'.
Area: Cal.R   Usage: Unknown   Status: Historical

The first signals on the Glasgow & South Western Railway were of the 'double vane' type, in use from the 1840s. As well as being able to show two red vanes for 'danger' (see [1.19]), the signals could display two green vanes for 'caution' [1.43]. In the 'clear' position, no vanes were visible, but a white light was shown during darkness (see [1.2]).

[1.43] Double Vane Signal showing 'Caution'.
Area: G&SWR   Usage: Unknown   Status: Historical