Section 6: Junction Signals and Route Indicators

On the LMS and LNER, the preference was for an alternative form of position light junction indicator with five white lights in each arm [6.46]. Following nationalisation, the five-lamp type was standard on all regions of B.R. apart from on the Southern Region, which stuck with the three-lamp variety (see [6.43]). Discussions took place in the early 1960s with a view to selecting one form of junction indicator as standard for use across all the B.R. regions. While the Motive Power Committee considered that the five-lamp type was the more effective option, the S&T Committee's preference was for the cheaper and simpler three-lamp indicator. The five-lamp junction indicator was finally accepted as standard although the Southern Region continued to install the three-lamp type until around 1966.

On the LMS, a miniature green signal (see [3.76]) could be provided to the left-hand or right-hand side of a main signal. In some cases, two miniature green signals could be provided on the same side, for routeing purposes. Where this occurred, each miniature green signal was provided with a miniature red aspect to be illuminated when the green light was extinguished [6.47], for the purpose of distinguishing which signal had cleared.

In later examples of colour light splitting distant signals, the single yellow aspects were displayed alongside each other at the same height [6.48]. It was considered unnecessary for the aspects to be at different heights when the junction signal ahead was at 'danger'.

In the 1985 resignalling of Crewe, several junction indicators were in fibre-optic form. A fibre-optic indicator, appropriately positioned to the left or right of the main aspect, could display a rectangular bar of white light at the angle required to represent a junction indication [6.49]. The same indicator could display an alphanumeric route indication if required for other routes.

In 1994, the junction indicators on two signals approaching Exeter St. David's station were altered experimentally. As an aid to determining the applicable direction of the junction indication, the 'pivot' lights on both indicators were fitted with a blue lens. Thus an illuminated junction indication appeared as one blue light and four white lights [6.52]. The blue pivot lights were removed and the standard white lights reinstated in 1995.

The 1996 principles changes also saw the introduction of the 'outer splitting distant signal'. In four-aspect signalled areas, the signal in rear of a splitting distant may be equipped as an outer splitting distant signal where routeing information needs to be given earlier than at the 'inner' splitting distant. Where an outer splitting distant is provided, the signal preceding the junction signal becomes known as the inner splitting distant signal. The outer splitting distant will display a double yellow aspect when the inner splitting distant is displaying single yellow and the junction signal is at red (i.e. normal four-aspect sequence). When the junction signal is cleared, the outer splitting distant signal will show a green aspect in one head and double yellow in the other [6.53]. The green aspect is on the side relating to the direction of route to be taken, and the aspects are stepped in height according to the relative speeds. The introduction of the outer splitting distant signal had been intended to make the preliminary route indicator (see [6.50 & 6.51]) redundant, however these would see further use, albeit under different circumstances. To date, no example of an outer splitting distant signal has actually existed.

In 2002, the principles for outer splitting distant signals changed again. The new principles saw a return to 1996 practice whereby one head would display a double yellow aspect while the other was showing green. However, the green aspect would be positioned higher or lower than both yellow lights in the other head [6.54], instead of being at equal height with one of them (see [6.53]).