Introduction

In normal Somerset & Dorset Joint Railway (S&DJR) signalling practice a ground signal would control only one route. For example, in the case of a ground signal at the exit from a set of sidings, where the 'trap point' led to a headshunt, the interlocking would permit the signal to be cleared only when the points were reversed for exit onto the main line. This means that any train shunting into the headshunt had to pass the signal in the 'on' position and one must assume that this was normal practice, as it is unlikely that signalmen were required to give flag signals for every such shunting move.

After the 1923 Grouping there were general discussions amongst the various Railway Companies about the undesirability of movements passing red signals and these talks gave rise to the change to yellow for distant signals as well as the idea of "yellow ground signals". Exactly when the latter were introduced is unknown, but probably it was circa-1925/26.

Use of Yellow Signals

In a "yellow ground signal" that part of the arm or disc normally coloured red is coloured yellow instead and there is a yellow light instead of red in the 'on' position. The yellow colour indicates to the driver that the signal may be passed in the 'on' position if the route for which it applies is not set. A typical use of such a signal would be in the example previously quoted above: if the points are normal, then a train may pass the ground signal in the 'on' position in order to shunt into the headshunt, but if the points are reversed then the signal must be obeyed.

Style of Signals

For all the original S&DJR installations of yellow ground signals the relevant Signal Instructions state that the signals were of the "miniature semaphore arm" type, with the arm painted yellow with a black band. This type of signal continued to be used specifically for this purpose long after the Southern Railway had introduced the "half disc" ground signal and "yellow discs" were not introduced by BR(SR) until the early 1960s. Consequently it is extremely unlikely that any of the S&DJR yellow ground signals were renewed as the disc pattern, although with the lack of photographic evidence it is not possible to confirm this. There are no known examples of a S&DJR Stevens 'drop-flap' ground signal being repainted with a yellow face.

Installation

Yellow ground signals existed at seven S&DJR locations prior to nationalisation in 1948. Six of these signals were installed in the period 1928-30, the earliest being at Masbury on 6-Nov-1928, and with one exception coincided with layout alterations. There were other S&DJR locations where such signals would have been appropriate, but were not installed, so perhaps existing practices were retained rather than incur additional expenditure. The final example was installed at Corfe Mullen Junction on 18-June-1933, with the difference that it was provided simply as an advance repeater signal for another (red) ground signal because of sighting difficulties.

The situation is a little unclear as to what further changes took place during British Railways days, particular after much of the northern part of the line was taken over by BR(Western Region). A signal diagram for Glastonbury in the 1960s shows that a further ground signal there had been converted to 'yellow' form (sometime after closure of the Wells Branch in 1951), but curiously also suggests that one of the existing yellow ground signals had been converted back to the normal 'red' form (even though its function has not changed). There is a reference also to yellow ground signals at Evercreech Junction South in a diagram for the 1960s, but photographic evidence (albeit black-and-white) does not seem to confirm this. Signal 17PULL at Blandford appears in the background of Plate 66 in Middleton Press's "Bournemouth to Evercreech Junction" - this photograph is dated 13-Aug-1965 and the signal was still of the 'miniature semaphore' type at that time.

Locations

The known examples of S&DJR yellow ground signals are listed in the table below in line order. The lever number of the signal is given, together with the number of the relevant Signal Instruction which described the introduction of the signal and the date of that work (where known). Details of any other examples would be most welcomed.

© Chris Osment 1998 & 2000
Signal graphic from Classic Software courtesy of John Hinson