Dorset Joint Railway
and other 'Rule 55 exempt' arrangements
This page provides information about the use of Diamond Signs and other 'Rule 55 exempt' arrangements on the former Somerset & Dorset Joint Railway (S&DJR).
In the old British Railways (BR) Rule Book, Rule 55 dealt with the situation when a train was detained at a signal that was displaying a 'stop' aspect. This was the longest rule in the book, but in simple terms the key factor relevant to this page was that, if a train was detained at a stop signal for more than 2 minutes (or immediately, during fog or falling snow), then the Fireman (or Guard or Shunter, as appropriate) had to go to the controlling signal-box in order to remind the signalman of the presence of the train and to ensure that it was protected properly. This was important in the days before the widespread use of devices such as treadles or track-circuits to provide an automatic indication in the signal-box of the train's presence at the signal, particularly if the train was out-of-sight of the signalman. Similarly, in an era long before the invention of mobile phones, the general lack of fixed telephones at signals meant that usually the only way to contact the signalman was actually to walk to the signal-box. Apart from being rather unpleasant for the person concerned during inclement weather, it could lead to a delay if the signal was cleared while he was away from the train.
Rule 55 covered a variety of situations on different types of lines with different types of signalling. It is important to note that the various references in RailWest to 'exemption' from Rule 55 apply only to the requirement for the Fireman, Guard or Shunter to go to the signal-box under normal circumstances - there was never a total exemption for all parts of Rule 55.
One solution to this problem was the provision of a treadle a short distance in rear of a signal, which would be depressed by an approaching train or light engine. If the treadle was operated while the signal was in the 'on' position, then it would activate a 'Train Waiting' indicator in the signal-box; the indication would be cancelled when the signal was cleared to the 'off' position. (This equipment tended to be provided mainly in conjunction with the Home signal of a signal-box, as any train waiting at the Home would be occupying the block section from the signal-box in rear.) It is known that this arrangement was provided at the Up Outer Home (No 15) at Midford and also at the Up Home (No 2) at Blandford.
In later years it became a more common practice to install a track-circuit in rear of a signal, so that the presence of any engine or train standing at the signal would be indicated electrically at the signal-box. There were several such examples on the S&DJR, which are listed in the separate RailWest Register of S&DJR Track-Circuits. It should be noted however that many such track-circuits were provided primarily for other purposes (eg to lock a signal or a set of points etc) and the ability to indicate the presence of a train waiting at the signal was a secondary benefit.
Another method was to provide a 'Fireman's Call Plunger' at the signal, where it would be housed in a small box fixed on the signal post. When an engine or train was detained at the signal then the fireman would get off the engine, go to the signal and press the plunger, which would operate an audible alarm and/or indicator in the controlling signal-box. This arrangement was provided at the Down Home (No 2) at Evercreech Junction North signal-box, where it appears to have been installed at an unknown date between 1941 and 1949.
On single-lines there was an exemption from Rule 55 if the Driver of the train was in possession of the relevant staff, tablet, or token for the single-line section. At some locations there might be an exemption specified in a printed Instruction, although no S&DJR examples are known. Elsewhere any exemptions might be indicated by means of an appropriate signal-post sign, as described below.
Clearly there would be little point in providing facilities to advise the signalman of the presence of a train waiting at a signal if the engine crew were unaware that they no longer needed to obey that part of Rule 55 which required them to go to the signal-box. As a result different railway companies adopted a variety of signs to be displayed at such signals and some useful background information can be found in Section 9 of the 'RailSigns' website .
At locations where a 'Fireman's Call Plunger' was provided then a 'D' sign was used and this is illustrated at  Item 9.5 . The broad left-hand section was fixed to the front of the signal post, so that the right-hand part projected to the side of the post and displayed a 'D' silhouette to the engine crew. The only known example of a 'D' sign on the S&DJR was fitted to the Down Home (No 2) at Evercreech Junction North, but there is no known photographic evidence to identify its precise style. It has been suggested that a 'D' sign was fitted also on the Down Home (No 6) at the temporary Waterloo Road signal-box (in use in 1946 and 1947 north of Shepton Mallet), but that has not been confirmed.
For signals that were exempt from Rule 55 for other reasons a 'diamond' sign was adopted by the Southern Railway (and others) in 1929 . Although known generally as the 'diamond sign', it was in fact an elongated hexagon shape (see  item 9.6) which measured 26.75"x12" and had a white face with a thin black border and a black rear. Usually the sign was fixed somewhere on the main signal post (often about eye level for the driver of an approaching train), but it was not unknown for it to be bracketed to one side. Where there were two or more stop signals on different 'dolls' on a bracket or gantry, then if all those signals were exempt from Rule 55 a single diamond sign would be fixed on the main post of the bracket or gantry, otherwise there would be separate signs on the dolls of the exempt signals only. There were several examples of diamond signs on the S&DJR and these are listed below.
Note: it is often stated in publications that the purpose of a diamond sign was to indicate the presence of a track-circuit. This is not correct - its purpose was to indicate exemption from Rule 55. Although it is probable that in most cases the exemption indeed did arise because of the existence of a track-circuit, there were other reasons for exemption (eg 'train waiting' treadles).
Midford: According to S&DJR Signal Instruction No 331 a diamond sign was provided on the Up Outer Home signal (No 15) on 4-April-1933, presumably because there was a 'Train Waiting' treadle in rear of that signal. This is the only known instance of the provision of a diamond sign being mentioned specifically in such S&DJR records. In BR days this sign bore a large black 'T' on its face to indicate that there was a telephone connected to the signal-box at that signal (see picture).
Midsomer Norton: There was a diamond sign on the Up Advanced Starting signal (No 13) in BR days . It is assumed that this was provided when a track-circuit was installed in rear of that signal at an unknown date in the 1950s, as there would have been no obvious reason for its existence prior to that change.
Masbury: In late 1928 a new siding connection (worked from a ground-frame) was provided in the Down line some distance south of the station. In connection with that alteration the Down Advanced Starting signal (No 4) was moved further south (and relocated to the Up side of the line) and a track-circuit provided in rear of that signal (S&DJR Signal Instructions Nos 287 & 289 refer). It is possible that a diamond sign was provided on that signal, either in 1928 or at a later date, but sadly there is no photograph of that signal currently available as confirmation, although it is noted that a diamond sign has been recorded in another publication .
Evercreech Junction South: In BR days there was a diamond sign on the Up Starting signal (No 20) and also one on the Down Starting (No 5). In the case of the latter signal, which had two co-acting arms, the sign was fixed on the bracket which supported the lower arm rather than on the tall post which carried the upper arm. By 1950 there were track-circuits in rear of both signals, but it is not known when the diamond signs were provided.
Templecombe No2 Junction: There were diamond signs on the Up Starting (No 9), the Up Advanced Starting (No 41) and the No 3 Jcn Intermediate Down Outer Home (No 29). The No 3 Jcn Intermediate Down Inner Home (No 28) and the Goods Down Home (No 42) were on separate dolls on the same gantry, so a single diamond sign applicable to both signals was placed on the down side gantry post. All those signals had track-circuits in their rear, which were installed when the signalling was altered in 1933 in connection with the closure of the No3 Junction signal-box. The diamond signs may have been fitted at the same time, or at a later date.
Given that there was a 'Train Waiting' indicator provided at Blandford in connection with a treadle in rear of the Up Home (No 2), it is surprising that the limited photographic evidence available from the BR period shows that no diamond sign was provided. One publication  records a diamond sign on the Up Advanced Starting (No 15) at Bailey Gate, but this does not appear in any photographs, nor does the known information about that location justify such a sign.
As the diamond sign was white, and usually the signal post to which it was fixed was painted white also, then it was the practice on some railways to paint a black band around the signal post behind the diamond sign in order to provide some contrast for better sighting. This appears not to have been the general S&DJR practice, although the photographic evidence is inconclusive in some instances and the arrangements at individual locations may have varied over time. At Midford there was no band on the lattice post of signal 15 in BR days, although older pictures of the previous wooden post suggest that a band may have existed then. There was a band on signal 13 at Midsomer Norton (actually a separate band on each of the two rails which formed the post). At Evercreech Junction South there was no band on signal 20, whilst on signal 5 the bracket to which the signal was fixed was painted in a dark colour anyway. At Templecombe (No 2 ) Junction there was a band on the main post of the gantry which carried signals 28 and 42, but apparently no bands on the posts of signals 29 and 41; no information is available for signal 9.
The author would welcome information about any other S&DJR 'diamond' or 'D' signs which are not listed in this page. Please send details by e-mail to RailWest, ideally with some dated photographic evidence.
© CJL Osment 2015-17
With acknowledgements to the late Ivo Peters for information from his photographic collection.