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.
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
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
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.
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.
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
This type of signal
is relatively rare, and is used only on goods lines and low-speed areas.
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
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
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.