At junctions, individual arms are generally provided to indicate which route a train is to take. The arms are usually mounted on separate posts (dolls) on a bracket or gantry, alongside each other. Combinations of the various types of signal illustrated in the preceding sections are used, according to the circumstances. The arms are generally arranged so that the higher arms apply to the higher speed routes, but occasionally the arrangement will indicate the importance of a route.
What is a junction? In railway terms, a junction can be anywhere where facing points allow trains to take different routes. Thus, as far as junction signals are concerned, there is no difference between the principles for signals provided at a junction with a branch line than those provided for connections between Fast and Slow lines on a multiple track route.
At a simple junction
A typical signal serving a simple junction has two arms. Here, the right-hand arm applies to the main line (fastest route) and the left-hand arm serves a branch or loop line.
Equal speed junctions
If the both routes have the same speed limit, the arms are placed level with each other.
The design of the bracket structure, whether it be “balanced”, or “left-handed” or “right-handed” is of no relevance to the signals’ meaning – that is all to do with giving the driver a good view despite curves, bridges and other obstructions.
More than two routes
This is a three-way junction signal, for routes of three different speeds or importance. An example of route importance would be where this signal was provided as a Slow Line home signal. Possible meanings might be:
- Fast Line to Goods Line Home
- Fast Line to Slow Line Home
- Fast Line to Fast Line home.
Routes into loops and sidings
Here is a three-way junction signal where one of the routes leads into a siding or loop. In this example, the miniature arm for the siding is mounted low on the post on its own bracket but it could also be mounted on the same bracket as the other arms.
Sometimes, a route into a siding or loop is controlled by a ground signal mounted at the foot of the main post. This arrangement was not typical with colour-light signals.
Occasionally, junction signals will be found with the arms mounted above each other. In this instance, the top arm always applies to the left-hand route and the bottom arm to the right. If there are more than two arms, they read left-to-right.
These are often called Stacked signals but it isn’t an official term.
This type of signal is relatively uncommon, and is used only on goods lines and low-speed areas. There is no equivalent with colour-light signals.
A way to indicate large numbers of routes, or overcome space limitations, is to provide a Route Indicator to accompany a single arm. These are only permitted in low-speed areas as the indications can only be determined from the driving cab at close range.
Splitting Distant signals
Sometimes, indications are given to drivers at the distant signal to show which route is being taken. These are called Splitting Distant signals. Here are some examples, many combinations are possible