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Severn Bridge Junction is the area of railway lines just south of Shrewsbury railway station, in Shropshire, England. It is controlled by a mechanical interlocked signal box of the same name, which is now the largest operational mechanical signal box in the world.[1] The Network Rail signalling area code is 'SBJ.'

Severn Bridge Junction signal box
The signal box as viewed from Shrewsbury station. Shrewsbury Abbey is in the background.
General information
TypeSignal box
LocationSouth of Shrewsbury railway station
Town or cityShrewsbury
Coordinates52°42′32″N 2°44′45″W / 52.70889°N 2.74583°W / 52.70889; -2.74583Coordinates: 52°42′32″N 2°44′45″W / 52.70889°N 2.74583°W / 52.70889; -2.74583
Construction started1903
ClientShrewsbury and Hereford Railway
OwnerNetwork Rail
Height38 feet (12 m)
Diameter95 by 11 feet (29.0 m × 3.4 m)
Technical details
Structural systemBrick and cement; slate roof
Floor count3
Design and construction
Architecture firmLondon and North Western Railway
DesignationsGrade II listed
Severn Bridge Junction as viewed from Shrewsbury Castle



The complexity of the railway system in the area is brought about by the convergence of five major lines at Shrewsbury,[1] built in the Victoria era by two competing and yet also co-operating railway companies, the Great Western Railway and the London and North Western Railway. They were competing to connect the coal and raw material supplies of South Wales with the industrialised Midlands and Northwest; and secondly to transport passengers to and from London to the port of Liverpool. After the GWR amalgamated with the Cambrian Railways in 1921, it was also a major point of accessing GWR services into Mid and West Wales:[1]

Lines formerly converging in the area also include the regionally important Severn Valley Railway (GWR), and the Stafford to Shrewsbury Line (LNWR).


A 1912 Railway Clearing House Junction Diagram showing (right) railways in the vicinity of Shrewsbury. Severn Bridge Junction is indicated as S.&H. & S.&W.'TON JN

The railway junction lies directly south of the railway station. It was constructed jointly by the GWR/LNWR after the completion of improvements to their jointly owned Shrewsbury and Hereford Railway, which at this location junctioned with the Wolverhampton to Shrewsbury Line. To allow freight trains to move to/from South Wales direct to the Midlands and hence avoid the passenger railway station, the junction was constructed in a tight triangular form south of the River Severn.

Signal boxEdit

Jointly constructed from 1902 to an enlarged standard LNWR design of 1876, the three storey structure is built of two storeys of red brick and cement, with a third floor mainly of wooden weather board pin-panel containing the glass windows, all topped by a Welsh slate pitched roof.[1] Access is via a door on the rear, with the lower two floors housing interlocking signalling equipment accessed via two internal wooden staircases.[1] The main operational floor houses a 180 lever interlocked frame, divided into two sections: Abbey Foregate to Sutton Bridge; Shrewsbury station to Crewe Junction.[1]

The frame scale makes it the largest remaining mechanical signal box on the British network, and from 2011 it became the largest mechanical signalbox in the world, following the closure of the 191 lever box at Spencer Street in Melbourne, Australia.[1]

Today only approximately half of the levers are in operational use, although it still takes two signallers to operate the complete system on a 24/7 basis, allowing 300 train movements per day.[2][1]


Although there have been line closures in the Shrewsbury area, and the closure of the joint Motive Power Depot at the end of the steam era in the 1960s, there is still a complex residual converging rail system in the area. Within 1 mile (1.6 km) of the junction, there are another five interlocked mechanical signal boxes:

  • Abbey Foregate Junction: located on the Wolverhampton line to allow access to the adjacent Abbey Foregate yard; its code is 'AF'.
  • Crewe Bank: closed 8 December 2012.[1]
  • Crewe Junction
  • English Bridge: controlled the southside of the triangular junction through Coleham to Sutton Bridge Junction. Closed in 1953, its controls were transferred to Severn Bridge.[1]
  • Harlescott Crossing: closed 8 December 2012.[1]

Network Rail currently believes that to simplify this system to allow it to be remotely controlled through coloured-light signals would not be economical.[1] Hence the current mechanical signalling system in the area is presently envisaged to remain in operation until at least 2030, and possibly as long as 2050 on current plans.[3]

See alsoEdit


  1. ^ a b c d e f g h i j k l Chris Milner (5 December 2012). "The world's largest signalbox". Railway Magazine. Retrieved 11 July 2014.
  2. ^ Stephen, Paul (July 2018). "FROM THE FILES: Shrewsbury's record-breakers". Retrieved 20 September 2018. This place is fairly unique these days in being double-manned, but with 92 levers to operate it keeps us fairly busy and you soon work through the shoe leather.
  3. ^ Railway Herald Issue 295, p8

Further readingEdit

  • Allen, David (3–16 December 1997). "Britain's longest 'box". RAIL. No. 319. EMAP Apex Publications. pp. 56–60. ISSN 0953-4563. OCLC 49953699.