Junction Signals and Route Indicators

LNER practice with regard to colour light splitting distant signals differed slightly from LMS practice (see [6.23]). One similarity was that when the junction signal was at 'danger', the splitting distant signal would display only one single yellow aspect when cleared. Another similarity was the two additional signal heads to indicate direction of divergence. However, in the LNER signals, both would illuminate together when the junction signal was cleared [6.34]. The head situated on the same side as the route to be taken would clear to green while the other showed yellow. If both routes were of a similar speed, the two lower lights were displayed at the same height [6.34], otherwise the lights would be stepped according to the relative speed of each route [6.35].

[6.34] Colour Light Splitting Distant Signal (e.g. junction signal ahead cleared for right-hand route) (routes of similar speed) (LNER).	[6.35] Colour Light Splitting Distant Signal (e.g. junction signal ahead cleared for (lower speed) right-hand route) (LNER).

A signal (numbered UC4B) had been installed in 1935 at Hackney Downs in the form shown in [6.35]. Later in the same year, this signal was converted from a three to a four-aspect signal, and the means of displaying routeing indications altered. The two directing distant indications were removed and replaced with special route indicator lamps, one on either side of the post. When the junction signal and the distant signal were both cleared, the latter would show an indication "F" or "S", applicable to the Up Fast or Up Suburban line, respectively. The indications were appropriately positioned relative to each other [6.36 & 6.37]. This form of advance route indicator was not replicated elsewhere, but was reminiscent of the suggestion in the IRSE Three-Position Signalling Committee's report of 1924 that certain colour light junction distant signals should be fitted with indicators that display either "L" or "R", for left-hand or right-hand route.

[6.36] Junction signal ahead cleared for route to Up Fast line (e.g. 'clear' aspect).	[6.37] Junction signal ahead cleared for route to Up Suburban line (e.g. 'preliminary caution' aspect).

In what was to become the standard form of colour light splitting distant signal, multiple signal heads are positioned side by side and stepped in height according to the relative speeds of the routes. This is the direct colour light equivalent of a splitting distant signal in semaphore form (see [6.5]). When the junction signal was at 'danger', the splitting distant signal (provided it was not itself at 'danger') would display a single yellow aspect in each of its heads [6.38]. When the junction signal was cleared, the appropriate head would clear to a higher aspect (double yellow or green) [6.39]. It was exceptional for a splitting distant signal to have three, rather than two, heads.

[6.38] Colour Light Splitting Distant Signal showing single yellow in each head (e.g. three heads).	[6.39] Colour Light Splitting Distant Signal (e.g. junction signal ahead cleared for a (lower speed) left-hand route, signal at 'preliminary caution').

In the Cheshire Lines Committee's 1935 resignalling of Manchester Central, a variant of the directing miniature colour light shunting signal (see [6.28 & 6.29]) was used where associated with a main signal (see also [3.67]). When cleared for the left-hand route, a green light was displayed above a letter "S" [6.40], and when cleared for the right-hand route, a green light was displayed below the letter "S" [6.41]. No aspect was displayed when the shunting signal was 'on'.

[6.40] Directing miniature colour light shunting signal associated with a main signal, 'off' for left-hand route (CLC).	[6.41] Directing miniature colour light shunting signal associated with a main signal, 'off' for right-hand route (CLC).

The LNER's experimental junction type route indicators at Thirsk (see [6.31 & 6.32]) were judged a success and became a standard feature, though in a modified form. The vertical indicator for the straight route (see [6.31]) was deemed unnecessary and was dispensed with, and future junction indicator arms comprised a row of individual white lights. This came about as a result of A.E. Tattersall's earlier experiments with position light type main signals (see [2.79 - 2.81]).

A maximum of three junction indicator arms could be provided to the left-hand or right-hand side of any signal. The six permitted junction indicator positions are referred to by number [6.42]. Positions 1, 2 and 3 are for routes progressively to the left of the straight route and positions 4, 5 and 6 are for routes progressively to the right. Junction indicator arms are commonly referred to as 'feathers'. The earliest position light type junction indicators were made up of three white lights in each arm [6.43]. The Southern Railway began installing this type from the 1936 resignalling between Waterloo and Hampton Court Junction. The LNER installed some of the three-lamp type in 1938 on the Chingford Branch resignalling scheme.

[6.42] Junction Indicator Positions.	[6.43] Three-Lamp Junction Indicator (e.g. Position 1).

A main signal with a junction indicator may also have a subsidiary signal (see Section 4) that can apply along the route(s) for which the junction indicator is provided. In some such cases, the junction indicator will be used when either the main signal or the subsidiary signal is cleared [6.44]. In other cases, where the junction indicator is only used with the main aspects, the subsidiary signal may have its own associated miniature alphanumeric route indicator.

A junction indication and an alphanumeric route indication can be displayed simultaneously at the same main signal [6.45]. This arrangement occasionally has to be resorted to in order to overcome the maximum three divergences on any one side that a junction indicator alone can refer to.

[6.44] Junction indicator used with a subsidiary signal (e.g. three-lamp junction indicator with 'calling-on' disc).	[6.45] Junction indication and alphanumeric route indication displayed together (e.g. three-lamp junction indicator with theatre type route indicator).

For a junction indicator to be equipped with both positions 1 and 6 or positions 3 and 4 is considered undesirable due to the risk that the indications may be mis-read. The arrangement shown in [6.45] may be used to avoid having either of these combinations of junction indicators at a signal.

Section 6: Junction Signals and Route Indicators

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