The Branch Line Society


Shrewsbury Area Signal Box Visits
Saturday 9th April 2016

Report by Ian Smith

All photos © Keith Flinders 2016, unless otherwise stated

13 participants met on Shrewsbury P3 at 10.00 to be greeted by Phil, the Local Operations Manager and two Mobile Operations Managers, Kev and John. Shrewsbury is a fascinating area, most of its railways have survived and it was a junction between LNW, GW (and even the Shropshire & Montgomeryshire Light*) Railways. The area has changed between 'Western' and 'London Midland' control over the years. There is still a variety of upper and lower quadrant signals and the different Company's signal boxes. It is a Mecca for signal boxes; five within a one-mile radius with the biggest collection of semaphores on NR. (*Former North Wales Jn.)

Participants were told the true story of the Shrewsbury P4 Wolverhampton-end bracket signal arms being changed from GWR pattern lower quadrant to standard BR upper quadrant. There was a local outcry but then it was then discovered that, due to the station canopy, the position of the arms could not be seen by station staff or train crew! Higher and lower signal posts were tried, but to no avail. There was even talk of cutting back the canopy but, as the station is listed another solution was required. In the end, 'OFF' indicators were provided and the upper quadrant arms remained.

Abbey Foregate Signal Box, the former large locking room glass windows were bricked up during WWII.

Note the six lines heading west (left).

Abbey Foregate signal box.

Abbey Foregate signal box is a 1914 built GWR brick to roof, hipped roof design, although the windows have been replaced by uPVC plain doubled glazed units. The 93-lever frame is original GWR with a number of white (spare) levers and spaces. It works Absolute Block to Severn Bridge Junction, towards Shrewsbury station and also over the Loop line (the station avoiding curve, now with only one booked train a week in one direction.). There are actually three double line block instruments:

   (1): No1 block instrument for No1 Up Main/Down Main line**.
   (2): No2 block instrument for No2 Up Main/Down Bay lines**.
   (3): 'Hereford' block instrument for the Loop line to English Bridge Jn.

**Thus there are effectively four running tracks between Abbey Foregate Jn and Shrewsbury station.

Towards Wolverhampton the lines are worked by Track Circuit Block to (since November 2012) the West Midlands Signalling Centre, Saltley. Train description on this line is by computer and VDU. Although there is no signal slotting or acceptance as such, Abbey Foregate's No1 Up Main Home (from P7) semaphore signal (No3) is released by Severn Bridge signal box clearing their No13 signal (a release/ interlocking lever), effectively the starter signal for the No1 Up Main line. If Abbey Foregate clears their signal first, Severn Bridge are not able to clear theirs and vice versa maintaining a safe method of operation. There are two GWR electric train route describers which, although no longer working, impressively still have their brass surrounds highly polished. All the points are mechanical but the original junction bracket signal just outside the box is now a colour light head with theatre light route indicator, replacing the former large rather splendid semaphore gantry.

The northeast aspect of the Severn Bridge Junction box never fails to impress.

Severn Bridge Junction box, (LNWR 1903) is the 'Holy Grail' for signal box aficionados and (since 2008) the world's largest operational manual box. It is in the centre of an extensive triangle of running lines, so an outsider (and even railwaymen not directly involved with it) could never have expected to gain access. Luckily for us, rail staff require a safe walking route across the track to the waste ground behind the box which, on examining signalling diagrams from the 1950s and early 1960s pinned up inside, once had a small turntable (visible as a circle of buddleia). With point rodding runs and signal wires disappearing at all sorts of weird angles, participants ascended the internal narrow staircases, up the two floors, passing the numerous and extensive interlocking bars, to the operating (third) floor. This gives a most interesting, very different view from usual of the station, railway layout and town.

One of the two identical signalling diagrams each end of the box; the layout is much simpler than the 1950s; P3, 4&5 are all occupied.

The frame is staffed by two signallers 06.00 to 22.00 daily (SuX) on 8-hour shifts and at all other times one. To this day, each signaller works one end of the frame, there being an 'imaginary line' splitting the territories in the gap between levers 88 and 91. There were tales of days gone by where duty signallers ('signalmen' then) would not even talk to each other. One told of the signaller on the end further from the toilet having to request permission to pass through the other signaller's domain to use it! The frame is 180 levers long; about half are in use including '1' and '180', with quite a few white (spare) levers but fewer spaces. Some with short handles are 'interlocking levers' and plated as such. They are the result of previous changes and no longer operate anything themselves but are part of the interlocking sequence.

The view from lever No.11 along towards No.180.

The alternative would be to relock the whole frame, which would be a mammoth task. The box interlocking diagram itself was enormous, just like a long roll of music for a full orchestra with lines (that look just like music staves) for each of the numerous vertical levels of the frame. The number of levels is one reason the box is so tall. This diagram also showed the detailed shapes of the cut outs and additions to the vertical and horizontal locking bars that fit into each other to 'lock' different moves in a fail safe way and must have been a very skilled job to design.

From outside, Severn Bridge Junction box appears to be narrower than normal, but this is just an illusion due to its tremendous height. The long and the short of it is that the box is 38ft tall, 11ft wide and 95ft long. The party were told that when the wind is blowing hard, the box shakes. The frame is the safest place to stand because LNWR practice was to fit the frames to uprights which were part of the box footings rather than attached to the structure. These large steel uprights could be seen as the group ascended past the massive locking frame. The box is Grade II listed, so the original windows are fitted with secondary glazing inside. There is also a false ceiling to reduce the drafts. There were several varnished wooden signal and point indicators on the block shelf as well as some LNWR electric train describers, with polished brass surrounds, unfortunately the latter not in use. Also not working was the famous double-faced clock between the two signalling positions. However, surprisingly, 'Train Ready to Start' instruments were available for both signallers, used by station staff if their radios fail. There are identical illuminated diagrams each end of the long operating floor, perpendicular to the frame rather than above it.

The frame is split into four sections, to accommodate the uprights and allow access to the windows. The two duty signallers explained how one controls station exits and the other Hereford line arrivals, although they could do either end if their colleague was tied up with something else. There are local bell codes for attaching or detaching in the through platforms (for example). P3 is bi-directionally signalled by 'acceptance levers' with Crewe Junction box. This prevents trains being signalled from both directions simultaneously. Very unusually this single line has a double line block instrument to Crewe Junction which can be used for either direction by either box, depending on whether the 'acceptance lever' is 'in' or 'out' of the frame. The interlocking required must be interesting (Victorian computers at their best)!

Another interesting feature is that Severn Bridge Junction has 13 Absolute Block worked lines. There are five to Crewe Junction, six to Abbey Foregate and two to Sutton Bridge Junction using seven double line instruments; possibly unique on NR (except perhaps at Stockport?) Although the Severn Bridge Junction layout is very compact and there is a general line speed of 15mph (or less), the latter means all distant signals are fixed and so there are no yellow (distant signal) levers in the frame. It is still a long (hefty) pull on the Down Hereford starter, which is also around a curve. The group could easily have stayed here all day and barely scratched the surface. The signallers advised that they receive three or four visits a year so we considered ourselves very privileged indeed.

Sutton Bridge Junction controls the junction between the Hereford route and the Cambrian route to Aberystwyth. Until September 1963 it was also the junction for passenger trains to the Severn Valley line to Bridgnorth and Hartlebury (etc). A headshunt was later retained to serve Shrewsbury Abbey oil terminal (CG 17 July 1988). Now, apart from the original bridge over the start of that route by the box, the track bed has been built over. It is another GWR brick built 1913 box, an original 61-lever frame with several white levers and a few spaces from the reduced layout under control. As with Abbey Foregate and Severn Bridge Junction, a blast wall had been built around the entrance door, and the locking room windows bricked up during WWII due to the local armament establishments.The box works Absolute Block to Severn Bridge Junction and, in the other direction, to Dorrington on the Hereford route with ETRMS to Machynlleth on the single Cambrian line to Welshpool. Surprisingly it can be switched out, leaving the signals clear for the Hereford route in both directions.

Sutton Bridge Junction signal box; left is the trackbed of the former Severn Valley line to Bridgnorth, latterly a headshunt for the Esso Oil Depot at the former Shrewsbury Abbey station. To the right of the box is the Hereford line to Dorrington, and off to the right is the Cambrian Line to Welshpool. The line far right is the headshunt for Coleham Depot. Beyond the bridge is the trailing crossover used last October by all trains from Shrewsbury to the Cambrian for a few days when the facing crossover was faulty. The third line (right of the crossover) is the Up Goods Loop (used by the 'Great Britain VI' on 22 April 2013, which the signaller on duty during our visit had signalled!). This end of the box shows the very thick WWII 'blast wall' built to protect the entrance and equipment.

Dorrington Signal Box (6m 25ch) was next, merely a section break with a trailing crossover (used quite frequently for Engineers' trains and single line working). It now has more white (spare) levers than the number in use, with the station and yard long since closed. Indeed the box is set well back from the railway following removal of the Down loop. It is an 1872 LNWR/GWR Joint Line design with a low hipped roof but has new double glazing units. The current frame dating from 1941 also controls an Intermediate Block Section on each line, useful at times of disruption and when freight traffic used to be heavier. The box is about halfway along the climb from Sutton Bridge Jn to just beyond Church Stretton. Dorrington also has a 'closing switch', normally used each night to extend the section from Sutton Bridge Junction (or even Severn Bridge Junction if the latter is switched out) to Marshbrook signal box, the next one south and beyond Church Stretton station. Church Stretton had a signal box that closed abruptly with severe flooding in the year 2000 and was not repaired. Marshbrook stays open as it controls a level crossing and was not visited but is another LNWR/GWR Joint Line design

The 11.30 Cardiff to Manchester Piccadilly, its far end is at Dorrington's crossover.

Craven Arms Crossing (formerly 'Long Lane Crossing') was the final visit. Sadly, its original life-expired timber structure was replaced by new plastic cladding in summer 2000, although the GWR equipment and frame remain in situ. The box is at a level crossing (which may be abolished) north of the station next to the facing crossover from the Down to Up lines used by trains to the Central Wales Line.

Craven Arms Crossing Signal Box looking south to the station. Once, there was a stone carriage shed on the right
(possibly originally a goods shed) where the BR Western Region Emergency Control Train was kept (secretly!).

The Central Wales Line token instrument is seen inside.

Central Wales trains all call at reversible Up P1 in both directions; Craven Arms Jn is to its south. Their train crews used to operate a local ground frame to access/egress the line and obtain/replace the token at a platform cabinet. Now the signaller issues and collects the token at the box speeding up the service. Surprisingly there were just two white levers in the 30-lever frame, although the detonator placer levers no longer operate. Craven Arms was the only location visited not to have BR standard plastic block instruments, retaining the varnished wooden GWR type, brass interlocking release buttons and lamp indicators. There was a 1967 gradient profile of the Central Wales Line showing where the signal boxes had been (their names crossed through), until rationalisation after the line was reprieved from closure in 1964.

This concluded visits to some fascinating signal boxes, controlling probably the largest collections of semaphore signals in the country. Thanks to the NR staff who showed the party round and to the friendly signallers who were more than happy to explain and answer the many questions. Particular thanks to Nick Garnham for all the arrangements. For most of the participants, a lifetime's ambition had finally been achieved.

A recent picture of Shrewsbury's fine Grade II listed 1848 station building floodlit.
[© Kev Adlam 2016]

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