signals (contd)
by John Hinson
 

junction signals

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.

	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.
	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/right-handed is of no relevance to the signals' meaning.
	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: Slow Line to Goods Line home Along Slow Line home Slow Line to Fast Line home.
	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.
	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. This type of signal is relatively rare, and is used only on goods lines and low-speed areas.
	Another way to indicate large numbers of routes, or overcome space limitations, is to provide a Route Indicator to accompany a single arm. As the signal is not as distinct as a multiple-arm junction signal, route indicators are only used in low speed areas.
Semaphore		Colour Light

Conditions are not always perfect, so it isn't always practical to install text-book signals. Curves in the line, bridges, buildings and station awnings can all have an effect on how good the view of a signal is to a driver.

A number of adaptations to standard signalling can be applied to achieve improved sighting. The simplest means (and the most common) is to simply make the signal taller or shorter, whilst another is to reposition the signal on the opposite side of the line.

Colour light signals do not present the same issues as semaphore signals as the signals themselves are far more compact and are thus easier to place in an appropriate position. In most cases, a standard colour light signal can be used as a replacement for the special types of signal described here.

		Sometimes, the view of a signal can be improved by bracketing it out from the signal post. This method is often used where the line is curved, and also where there isn't room to position the signal alongside the line to which it applies.
Lower quadrant	Upper quadrant		Colour Light