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Section 6: Junction Signals and Route Indicators

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Where a main signal can lead to more than one destination, the driver needs to be informed of the route that will be taken so that the speed of the train may be regulated through the junction. An indication of route may also be given in association with a shunting signal.


Routeing 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 was 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. *
Area: All Areas   Usage: Unknown   Status: Historical
[6.2] Semaphore Junction Signal. *
Area: All Areas   Usage: High   Status: Current
Note: The above illustrations serve only to show the positions of the signal arms. For full details of their appearance, refer to Section 2.

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]. In some early examples, the arms of junction signals were mounted on separate posts placed on opposite sides of the railway.

The need to identify the relative importance of each route remains and can be achieved by stepping the signals in height if they apply to routes that differ in speed. The highest signal applies to the fastest route and subsequent signals on either side are progressively lower [6.4].

[6.3] Semaphore Junction Signal. *
Area: All Areas   Usage: High   Status: Current
[6.4] Semaphore Junction Signal. * Click Here for Photo
Area: All Areas   Usage: High   Status: Current
Note: The above illustrations serve only to show the positions of the signal arms. For full details of their appearance, refer to Section 2.

The distant signal on the approach to a diverging junction might also have multiple arms. These were termed 'splitting distant' signals and their distant arms were 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 shown in [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. The last semaphore splitting distant signal, at Larbert Junction, was abolished in 2007.

[6.5] Semaphore Splitting Distant Signal. * Click Here for Photo
Area: All Areas   Usage: High   Status: Historical
[6.6] Semaphore Splitting Distant Signal. *
Area: All Areas   Usage: Low   Status: Historical
Note: The above illustrations serve only to show the positions of the signal arms. For full details of their appearance, refer to Section 2.

If other stop signals intervened between the distant signal and the junction signal, then those signals might also be given multiple stop arms to repeat the routeing information. This practice was relatively prevalent on the Great Western Railway and the London & North Western Railway.

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.
Area: All Areas   Usage: High   Status: Historical
[6.8] Semaphore Junction Signal with Description Boards.
Area: All Areas   Usage: High   Status: Historical

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

[6.9] Semaphore Splitting Distant Signal with Indexed Arms.
Area: Various   Usage: Unknown   Status: Historical

Shunting signals frequently had no indication of route associated with them and the same signal could therefore apply to a number of different routes. Where route indications were necessary, 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 generally depended on 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). Click Here for Photo
Area: All Areas   Usage: High   Status: Obsolescent
[6.11] Shunting Signals one above the other. Click Here for Photo
Area: All Areas   Usage: High   Status: Current
[6.12] Indexed Shunting Signals.
Area: Various   Usage: Unknown   Status: Historical