Liverpool Street (Central) signal cabin

Liverpool Street (Central)
LB
Overview
Opened	30 July 1900
Closed	11 December 1999
Operator	London Underground

Liverpool Street (prefix LB) was a signal cabin located within the station of the same name on London Undergrounds' Central line at Deep Tube level. Opened in 1912 it closed in 1999 as part of a re-signalling programme. The 1937 lever frame now operates as Bolton Abbey signal box on the Embsay & Bolton Abbey Railway, North Yorkshire. It is not to be confused with the signal cabin within the same station at Sub-Surface level.

Central London Railway

The original signal cabin came into use on 28 July 1912 as the terminus of the eastward extension of the Central London Railway (CLR) from Bank to Liverpool Street. The signal cabin (prefix A) was situated at the eastern end of the platforms and was equipped with a Westinghouse B-style miniature frame of 15 levers. The comparatively small lever frame was reflective of the modest two-track terminus it operated, a consequence of the high costs the CLR incurred building the Liverpool Street extension which passed under some of the most historic and expensive real estate in the country.

London Transport

In 1933, London Passenger Transport Board was formed operating under the public brand of London Transport (LT). This corporation unified the previously independent underground lines which brought with them an array of different operating practises including rolling stock, civil engineering, permanent way and signalling. A new signal cabin (prefix LB) was opened on 31 October 1937 some 70ft distant of the previous one but located in a similar narrow cross passage between the platforms. The cabin was equipped with a Westinghouse B/K-style miniature frame of 23 levers, aesthetically similar the previous B-style with minor technological differences.

New Works Programme

As part of the New Works Programme enacted in 1933, the Central line was due to take over part of the London & North Eastern Railway (LNER) steam operated services between Liverpool Street, Hainault, Woodford, and Ongar which we’re struggling to cope with increasing demand. This takeover required the excavation of tunnels east of Liverpool Street to link up with existing lines at Leyton and Newbury Park. Construction was well underway by the outbreak of WW2 and continued incrementally until 1940 when they were requisitioned by the War Office. The unfitted tunnels between Leytonstone and Newbury Park were used by the Plessy Company for the manufacture of aircraft components whilst tunnels and incomplete stations in Inner London areas became civilian air shelters. After hostilities ended in 1945, fit out of stations and permanent way resumed with services to Leytonstone, Woodford and Newbury Park starting in 1947 ending Liverpool Streets 35-year tenure as the easternmost terminus of the Central line. A pair of reversing sidings were also constructed between the new eastward tunnels with the existing lever frame receiving modifications to reflect the new layout.

Post-war peak

The years between 1945 and the late-1960’s would come to mark the zenith of signal cabins on London Underground reaching their maximum proliferation as the technology to concentrate signalling control into a single facility was still too costly to pursue and develop in the cash strapped years immediately after WW2. Despite the difficulties London Transport faced in completing the now rationalised New Works Programme, the suburban extensions of the Central line into Essex and Middlesex proved to be a resounding success. The increase in patronage was such to an extent that by the 1950’s, the Central line was operating an intensive service with trains every 2 minutes in Central London, not too dissimilar to the frequency today.

The operation of such an intensive service was helped by the developments in signalling that Westinghouse had continued to develop with the CLR and later LT which included innovations such as ‘multi-home’ signalling. Instead of signals being spaced to accommodate the length of a single train, track block sections where split into multiple smaller lengths with speed-controlled signals allowing trains to creep forwards at reduced headways whilst staying a safe distance apart. Whilst this was by no means unique to the Underground, the early adoption of this signalling arrangement coupled with the favourable topography of the route made it an early pioneer of what Automatic Train Operation (ATO) now emulates. Despite the marked decline in patronage the Underground suffered in the 60’s, 70’s and 80’s, the Central line maintained an intensive core service thanks in part to the foresight of the CLR to provide reserving sidings at multiple strategic locations. At a time when services across the network were being thinned as an economy measure, the sidings at Liverpool Street saw regular use by shuttle services between the City, Marble Arch and White City during off-peak hours.

Closure and Preservation

By the 1990’s, patronage on the Central line and wider Underground network was rebounding again. With signalling equipment on the Central line deemed to be life expired and increasingly unreliable to operate, London Transport developed a digitised signalling system capable of Automatic Train Operation (ATO) using off the shelf components from Westinghouse to be deployed in conjunction with the roll out of a new fleet of 1992 stock. Whilst ATO systems had been successfully deployed on new build metro lines since the opening of the Victoria line in 1969, the application of this technology to a pre-existing railway with legacy signalling was hitherto unheard of. As a result, it would take from 1996 until 2002 to migrate all elements of the Central line from legacy signalling to ATO closing all the existing signal cabins on the line in the process.

On 10 March 1999, a temporary Push-Button Desk superseded the lever frame at Liverpool Street (Central) within the confines of the existing signal cabin and controlling the same area. During this brief period of hybrid working, a Signalling Equipment Room (SER) was commissioned with Computer Based Interlocking (CBI) on 10 March 1997. CBI, a form of solid-state interlocking, replaced the electro-mechanical interlocking located under the superseded miniature lever-frame. Liverpool Street (Central) signal cabin eventually closed on 11 December 1999 with its area of control being absorbed by Wood Lane Service Control Centre and ATO being commissioned in the area between February and March 2000.

Following closure, the 1937 Westinghouse B/K style lever frame was salvaged by the Embsay & Bolton Abbey Railway, North Yorkshire. It was restored, re-locked and now operates as part of the Midland Railway signal box at Bolton Abbey.