Ground and Fixed Signals
There is a photo of a full-disc ground signal used at Hale in Cheshire in Appendix 5 - Hale Station - Cheshire Lines Committee
From quite early on it was realised that the standard signal, mounted on a post and visible at considerable distances, was not required when shunting. Also it helped if the train driver could see which way points had been set as he approached them.
Various types of small signal, mounted next to the track and called 'ground signals' were developed. One less common name for these was 'dwarf signals' and the signal man at my local station told me the railway staff called them 'Dolly' signals.
The first ground signals were simple discs mechanically linked to points so as to indicate which way the points were set. If the disk was facing you it was set for the turning, if edge on it was set for straight ahead. Then came oil lamps, fitted with two lenses and mounted on a pivot so that either the red or the white lens could be turned to face the driver. To aid day-time working it was a common practice to add a large red painted plate or disk of metal round the red lens, but this was not universal.
Some companies, including the GWR and LNWR, tried very small semaphore type ground signals, again with a lamp behind to give a clear indication at night, however these proved difficult to see.
Fig___ Examples of early pattern Ground Signals
Early ground signals were operated by the point blades themselves. The danger is of course that the points might not have fully closed, so 'independent' signals were developed. These appear the same to the train crew but they are operated by a separate lever from the signal box or a local lever via wires and pulleys. The point mechanism was fitted with a hole and pin arrangement such that the signal could only be moved to the all-clear when the point blades were fully home. The photograph of the double ground signal (Fig___) shows the locking mechanism which is always mounted beside the relevant point as it is operated directly by the blades. In the shown example the mechanism is very close to the signal but it could equally be some distance away. The mechanism consists of a plate about eighteen inches (45 cm) square with a rod leading to the point blades and two rods running parallel to the track. The signal control wires are connected via the two rods and these can only be moved when the bar to the point is in the correct position.
Fig___ Ground signal interlocking mechanism
At about the time of the First World War a new design appeared, consisting of a more or less circular plate perhaps a foot in diameter, usually painted white with a red stripe across the middle.
The disc was pivoted in the centre so it could rotate, on early examples the disc was bolted to the arm of the miniature semaphore signal. When the red stripe was horizontal it meant stop, when at forty-five degrees it meant all-clear, for night operation small holes with coloured glass lenses were fitted to the plate and an oil lamp mounted behind to give a clear indication.
These rotating disk signals could be either upper quadrant or lower quadrant depending upon the preference of the owning company.
Where the original pivoting oil lamp signals still existed (the LNWR had quite a few of these for example), two separate discs were sometimes added to the two faces of the lamp. One plate had a horizontal red stripe, the other had a diagonal stripe, representing stop and all clear respectively, these plates had a hole in the centre for the original oil lamp lens. Some of these modified oil lamp signals survived into the 1960's.
There were variations in the design of disc signals, the LMS and the Southern Railway both had rotating discs consisting of fractionally more than half a circle with a flat bottom, the SR type had a slight dip along the lower edge, the LMS had a straight bottom edge. There were a couple of the LMS type still in use in 1997 at Stockport railway station south of Manchester. The GWR started with a similar flat bottomed shape (they only cropped off about the bottom third of the disk) but then used a full circle, and I believe this latter type became the standard for British Railways. The LNER standard upper quadrant ground signal was a full disc. These disc signals did not replace all the older designs, examples of the LNWR ground semaphore type remained in use into the 1970's and possibly the early 1980's, however where British Railways replaced ground signals they fitted the disc type.
Ground signals were only used for shunting purposes so the prohibition of two arms for different tracks on a single post did not apply, hence you will see disc signals 'stacked' two, three or even four high on a single short post. I believe there was a single example of a five disk signal (five disks mounted one above the other on a single post). The three disk type shown below was at the entrance to the DMU stabling sidings at Stockport, south of Manchester.
Fig___ Three-high disc type ground signal
As with the multiple home arms these are read from top to bottom as referring to routes from left to right, hence on a two disk signal the top disk refers to the route to the left and the upper disc that straight ahead or to the right. Multiple pivoted oil-lamp signals could not be mounted on a single post and where there was insufficient room for these to be placed side by side they were mounted separately one behind the other, with the rear lamp mounted on a longer spindle to show over the top.
The convention is to mount the signal, of any type, to the left of the track it controlled. Where a single disk was mounted between two sidings and it would be unclear which track it applied to a small white painted metal plate with a black arrow was added below the disk to show which track it referred to.
Ground signals showed red for danger and green or white (prior to 1893) for all-clear but, due to the proliferation of red ground signal lights in crowded yards, several companies used a white light for danger from about the time of the First World War. In the late 1920's the LMS and possibly other companies began using yellow lights and yellow miniature arms on ground signals which might be passed at 'danger' for shunting purposes.
Modern British Railways disc type ground signals have a small electric lamp in a housing to the upper right of the disk which illuminates the disk at night. The reverse side of the disk signal has a simple white semaphore arm, although this is only of real use where the rear of the signal is visible from the local signal box.
Fig___ Disc type ground signals
Ratio offer a kit of the later GWR/British Railways rotating disc signal in a pack of four single discs, these were unobtainable for a while so I made some up using a leather punch to make 2 mm diameter disks from 20 thou card.
To do this punch several disks with the punch, these will 'back up' inside the punch tube. Insert a panel pin into the punch and operate the mechanism to push the cut discs out of the tube. You may then need to put them between two sheets of metal (I used thick washers) and squeeze them flat with pliers or a gentle tap with a hammer. The discs were then stuck to a 6 mm length of 30 x 30 thou Slaters plastic rod. The lamp was a 2 mm length of 1 mm diameter round section rod carved about the top to represent the chimney. For the double disk type use an 8 mm high support and use 2 mm length of the same 30 x 30 thou rod to represent the square bodied lamps.
The ground signals in use at Stockport station on the London-Manchester line are an LMS design dating from the 1940's. The frame is from pressed metal and there is a small lamp on an arm which illuminates the front face of the signal. These signals were designed for use with the standard LMS cropped circle disks but the mountings are arranged at an angle so that on multiple disk signals full disks can be fitted with the top of the lower disk overlapping the base of the one above. In the 1990's all these signals retained the original cropped LMS disks.
Fig___ Photographs of disk type ground signals in 1997
Some signals would always remain in one position, for example some 'distant' signals at the approach to a difficult junction were fixed at the danger position. On these the arm was simply screwed to the post. The arm often carried no spectacle plate with its coloured glass, instead the lamp itself was fitted with a green or yellow glass, where upper quadrant signals were used the spectacle plate could be retained as shown in the sketch..
In this category we also find 'whistle' signs, which told a driver to sound his whistle. These were mounted where there was any danger of a train surprising someone, such as un-gated level crossings on light railways and industrial lines. If a shunting line passed under a bridge or through an arch in a viaduct a 'whistle' sign might be mounted so people on the far side of the obstruction would be warned of the trains approach. Most common was a simple board with the word WHISTLE painted on it, the GWR used a circular board painted red and with the letters SW painted on it. British Railways used a circular board about eighteen inches in diameter with a red ring around the edge and a black 'W' on a white centre.
Other fixed signals include the speed restriction sign, used to warn drivers of reduced maximum speeds across viaducts and bridges, when approaching unusually tight corners or where track was likely to be below the normal standard perhaps due to maintenance work. As far as I am aware the SR and LMS did not use fixed, permanent, speed restriction signs however the GWR employed a circular board with the maximum speed. The LNER employed numbers cut from steel plate and this design was adopted by British Railways. These consist of cut-out steel numbers approximately eighteen inches high mounted on a metal post about five foot high. The LNER painted the numbers white but BR favoured yellow (I believe this change was introduced in the mid 1960's as it was at that time that British Railways research indicated that yellow was an easier colour to see than red). When these are placed between tracks where confusion might arise they have a cut-out metal arrow welded to the support post just below the numbers.
Following privatisation Railtrack adopted a circular white plate about two foot (60cm) in diameter with a red ring around the edge and the speed limit in black numbers. These are virtually identical to the speed restriction signs used on the roads.
Temporary speed restrictions were sometimes imposed, notably where work was being done on the track. The start of the restriction was marked with a portable sign showing either the letter C or the maximum speed, the end of the restriction was marked with a similar sign showing the letter T. I believe most such signs were square as shown however the GWR used a circular C sign. According to Glanville Carlton the early BR "C" and "T" signs were, in fact, stencils, which were slid into special oil lamps which had a large 2ft (?) cowl, fitted with an opal white plastic 'glass'. The end result was surprisingly visible at night.
To warn drivers that a temporary restriction lay ahead an arrow shaped board about three feet long was positioned further down the line. The board had two holes, about two feet apart, behind which coloured lights were mounted. The board was positioned about half a mile behind the works (that is half a mile before the train would reach the work area) and displayed a green and white light. According to Glanville Carlton the early BR (and possibly immediately pre-nationalisation) arrow boards were painted yellow and had two yellow oil lamps mounted behind the board, however, according to my notes British Railways initially used a green painted sign as shown in the sketch (into the 1960's) but one seen in the late 1980's was painted white with two flashing yellow lights (presumably the standard battery powered type used on roads at that time).
Beside the track there were, and are, the gradient posts. Short posts with two arms pointing along the track, one in each direction, giving a simple indication where the gradient changed. These were quite small, perhaps three foot high with two foot long arms. The post and arms were painted white and the actual gradient was painted on the arms in black.
Finally with the introduction of electric and diesel multiple units British Railways introduced small signs, usually attached to lamp posts, on the platforms indicating where the driver should stop for various coach formations. These were black, about a foot high by eight inches wide with white lettering. With steam hauled trains there would usually be either just a couple of coaches or quite a few, so the driver either stopped somewhere about the waiting room or at the far end of the platform, the DMU and EMU drivers must have found it difficult to judge where to stop. There would typically be one of these small signs for a four car unit and another father along the platform for a six car unit.
Fig___ Some typical fixed signals