This article (slightly modified from the one which appeared in the Winter 1998 edition of Bluebell News) is not intended as an in-depth highly-technical review of signalling practices, more a source of general information about this complex subject and how it affects the Bluebell Railway.
In the earliest days of railways, trains were not really regulated at all - they were despatched at intervals with a minimum time allowed between them. As railways grew and technology improved, both the number and speed of trains increased, leading to inevitable mishaps. To try to regulate things better, Railway Policemen were employed and they were literally a form of human signal, policing the traffic on their line and endeavouring to keep the trains a safe distance apart. (They were, naturally, nick-named "Bobbies", a name which was subsequently inherited by Signalmen and is still in use to this day). The human knack for misunderstanding and error soon led to the development of a form of mechanical signalling controlled from a central point, the signalbox.
Much improved as this system was, there were still plenty of opportunities for error, leading to many well-documented accidents, so that eventually Parliament had to intervene and formally regulate the various railway companies to make them safer. There have been many, many different Acts of Parliament covering all topics of safety but probably the most important was the Regulation of Railways Act of 1889 which made compulsory: block working (making it impossible for more than one train to occupy any one "block" of track), interlocking (making it impossible to set a conflicting route, or signal a route other than the one set), the locking of facing points and the continuous train brake. This meant a lot of work for some of the railways, such as the Cambrian, which had (through their dire financial conditions) been unable to make much effort to improve the safety of their lines. The LB&SCR was one railway at the forefront of railway safety, having had the misfortune of some spectacular accidents early in its life!
Large railways developed their own systems whilst smaller ones would purchase "off the shelf" from companies such as McKenzie & Holland, Saxby & Farmer or Westinghouse. But, different as their appearance might be, the basic functions were all the same. By and large you can divide signals into three categories, running signals which control trains along their route, shunting signals which control movements over short distances and information signals. Here are described the various types you can see along the route of the Bluebell:-
1. Running Signals.
Fig.1 Stop Signals at the north of Horsted Keynes Station.
Stop signals are normally an arm with a red face and a white
stripe on the front whilst the reverse is white with a black stripe. Fig.1
shows the Stop signals controlling the exit north from platforms 3 & 4 and
5 at Horsted Keynes, and the two First Advanced Starting signals by the bridge
in the background. (Note the white-painted brickwork behind the signal arms, to
help make them visible). Caution signals are usually "fish-tailed"
and painted yellow with a black ">" stripe on the front and
white with a black "< " stripe on the reverse. When a
signal's arm is horizontal it is said to be "on" and when it is
either raised or lowered, it is said to be "off".
Fig.3 Left: The upper quadrant Inner Home signal
controlling entrance to Horsted Keynes station from the south.
Fig.4 Right: The lower quadrant Advanced Starting signal at Sheffield Park that allows entry to the single line section.
In the early days most signals were lowered to the "off" position and are called lower-quadrant but there were some accidents caused by broken signal wires allowing the arm to fall when it shouldn't which led many railways to adopt the raised arm, or upper-quadrant signal. (Note the different arrangement the two designs of signal have for the spectacle plates that show a coloured light after dark). Those that stayed with the lower-quadrant arm introduced a weight to counter the weight of the signal arm so that if the wire were to break the signal would remain at danger. Subsequently the counter-weight was introduced to upper-quadrant signals as well. A few railways had a rather complicated "somersault" arrangement whereby the signal arm would pivot, away from its post, through 90 degrees so that when "off" the arm was vertical. The Bluebell has examples of both lower quadrant signals as used by the LB&SCR and upper quadrant signals as used by the SR. Signalposts can carry more than one arm, the most common forms of multi-arm signal being those with a Stop arm at the top and a Distant arm below, and the bracket signal.
The bracket signal can carry two or more raised posts, arranged according to the route they control. The "main" route will always be controlled by the signal on the highest post so if a bracket signal controls a junction with a branch line or siding leading off to the left, then the main route will be controlled by the higher arm, usually mounted on a post directly above the supporting post below the bracket, whilst the line branching off will be controlled by the signal on a shorter arm, off-set to the left. (A bigger development of the bracket signal is the gantry signal, spanning several tracks, where the route controlled is identified by reading the signal arms from left to right, the importance of the route being reflected by the height of the signal arm. We do not have a gantry signal on the Bluebell). Where a single post carries two or more Stop arms, (as in Fig.5, left,the home signal just south of Kingscote station) then as you read the arms down the post from top to bottom they apply to the routes from left to right. In this photograph the road is set for the train to enter the "main" (one day to be the "up") platform at Kingscote station.
common, use of more than one arm on a signalpost is where there are both Home
and a Distant signal arms. Fig.6, right, shows the down outer home for
Horsted Keynes with, in addition, a repeater arm for the Home signal. These
are used in situations where there is a problem sighting a signal, usually
because the driver would not see it until he is almost at it, so the
"main" arm is the higher one whilst the lower one is the repeating
one, easily seen from the cab of a locomotive standing at the signal. The
Caution signal beneath the Stop signal is permanently in the Caution position
and is known as a Fixed Distant, though will be a working signal when the
re-signalling of Horsted is complete. For night use the signals will display a
green light when "off", a red light for a Stop signal which is
"on" or a yellow light for a Distant signal which is "on".
A Fixed Distant can, of course, only ever have a yellow light.
Fig.7, left. The bracket Starting signals at the north end of platform 3 at Horsted Keynes (photographed by Paul Pettit during engineering works to relay some track). The righthand arm is on a taller doll as it refers to the through route. The lefthand arm is lower as it refers to the route via the loop line.
Fig.8, right. The equal bracket, lower quadrant, Inner
Home signals at the approach to Sheffield Park. Photo: Adrian Lee. Both
lines are of equal status so both signals are the same height and mounted on
posts set an equal distance from the supporting post. The lower arms are known
as "calling-on signals" and permit movements past the signal when the
platform line is occupied.
2. Shunting Signals.
The most common ones are rotating discs, (as in Fig.9, left, SR Westinghouse pattern disc signals at Sheffield Park. The one on the left is "on" whilst that on the right is "off") either white with a red stripe or yellow with a black stripe, and arms which are a smaller version of the Stop signal arm, (as the two righthand arms in fig.10, right, Shunt arms for the Ardingly siding at Horsted Keynes) sometimes with a letter, often with a circle attached to their face (as in fig.8 above).
Figs. 11a, left, and 11b, right.
When "on" there is a red aspect with a white hand
pointing to the track it protects and when "off" a green aspect with
a white cross.
The function of a shunting signal is simple, when it is
"off" it permits the driver to pass, but unlike a running signal,
only for as far as he can see the line to be clear. It does not necessarily
give him permission to proceed as far as the next signal and he must be
prepared to stop at any time after passing the signal. If the signal is yellow
with a black stripe, then it may be passed when "on" providing the
movement is not in the direction controlled by the signal, which avoids the
need for lots of shunt signals in sidings which can be safely operated by a
shunter. At Horsted Keynes there was such a yellow and black shunt signal which
controlled movement out of the down sidings, enabling movements to take place
within the sidings whilst it was "on" providing they did not entail
leaving the sidings. This has been temporarily replaced with a colour light
Position Light signal and will be replaced by a white disc with a red stripe,
which must be obeyed for all movements.
Fig.12, left. The lever frame in Horsted Keynes signalbox.
Fig.13, right. The ground frame (now abolished) that was at the north of the station.
3. Information Signals.
Fig.14, left. A railway milepost. Distances on the Bluebell are measured in miles and quarter miles from Culver Junction.
Fig.15, right. The sign giving advance warning that there is a speed
Fig.16a, left and Fig.16b, right. Two alternative signs advising the
driver of the commencement of a speed restriction.
Fig.17, left: Termination of speed restriction sign.
Fig.18, right: It does what it says on the tin!
Your ideal Film/TV location?