Section 6: Junction Signals and Route Indicators

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Where there is more than one available destination ahead of a main signal, the driver needs to be informed of the route which is to be taken so that the speed of the train may be regulated through the junction. This information was originally conveyed by having a separate signal for each route and placing them one above the other on one post. The signal for the main line would be placed at the top of the post with the other signals placed below in descending order of importance [6.1]. That arrangement was fine from the point of view of an express train driver, who knew that the top signal was the one that applied, but for drivers of other trains it could be confusing. The practice was altered such that the uppermost signal applied to the line on the extreme left regardless of its importance. The second signal from the top applied to the next line in order from the left and so on [6.2].

[6.1] Semaphore Junction Signal. *	[6.2] Semaphore Junction Signal. *

The Board of Trade favoured the above arrangement, but from the early 1860s, the preferred arrangement for high speed running was to place the signals side by side in an order corresponding to the direction of each route [6.3]. It remained a necessity to identify the relative importance of each signal. Where the signals apply to routes that differ in speed it is normal for them to be stepped in height. The highest signal applies to the fastest route and subsequent signals on either side are progressively lower [6.4].

[6.3] Semaphore Junction Signal. *	[6.4] Semaphore Junction Signal. *

In some cases, the distant signal on the approach to a diverging junction may also have multiple arms. These are termed 'splitting distant' signals and their distant arms are arranged in the same configuration as the stop arms of the junction signal. For example, if a splitting distant signal was provided in rear of the junction signal shown in [6.4], it would appear as [6.5]. Exceptionally, distant arms could be placed one above the other on the same post [6.6]. The provision of splitting distant signals was at one time a requirement of the Board of Trade. On 17 September 1912, a derailment occurred on a diverging junction at Ditton (London & North Western Railway). The splitting distant signal was 'off' for the diverging route, but the driver had mistaken it for the straight route's distant and took the junction at too high a speed. As a result of this, from 1914 the BoT required that splitting distants should only be provided in exceptional circumstances.

[6.5] Semaphore Splitting Distant Signal. *	[6.6] Semaphore Splitting Distant Signal. *

If other stop signals intervened between the splitting distant and the junction signal, on some railways (especially the Great Western Railway) it was the practice for those signals to also have multiple stop arms.

It was quite common in the early years for junction signals to have 'indexed' arms. These had the signal applications written directly on the front of each signal arm [6.7]. As an alternative to indexed arms, the signal applications could be exhibited on boards below each arm [6.8].

[6.7] Semaphore Junction Signal with Indexed Arms.	[6.8] Semaphore Junction Signal with Description Boards.

Splitting distant signals could be fitted with indexed arms [6.9].

[6.9] Semaphore Splitting Distant Signal with Indexed Arms.

Shunting signals often did not have an indication of route associated with them and one signal could apply to many routes. Where route indications were required, multiple signals could be placed side by side (and possibly stepped in height) [6.10] or stacked one above the other [6.11]. The choice was generally dependent upon the form of signal used or the space available on site. Very occasionally, shunting signals were indexed [6.12].

[6.10] Shunting Signals side by side (and stepped).	[6.11] Shunting Signals one above the other.	[6.12] Indexed Shunting Signals.

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