Liverpool Street interlocking machine room
| Liverpool Street IMR | |
|---|---|
| OD | |
 | |
| Overview | |
| Opened | 1 February 1875 |
| Closed | 6 March 2021 |
| Operator | London Underground |
Liverpool Street (prefix OD) is a Grade II listed Interlocking Machine Room (IMR) and former signal cabin located in the station of the same name on the Circle, Hammersmith & City and Metropolitan lines of London Underground’s Sub-Surface Railway (SSR). Opened in 1875 and converted to remote operation in 1956, it closed on 6 March 2021 as part of the Four Lines Modernisation (4LM) re-signalling programme. It is not to be confused with the former signal cabin located on the Central line within the same station at a lower level.
Metropolitan Railway[edit | edit source]
Liverpool Street signal cabin opened with the Metropolitan Railway’s (MR) dedicated station at Bishopsgate on 1 February 1875.[1] For the first year of the extension east of Moorgate, MR trains had run into the Great Eastern Railway (GER) station.[2] The signal cabin was originally equipped with a full size lever frame of 40 levers.[3] In keeping with early Underground signal boxes, it mimicked mainline railway companies of the period with gabled canopies and intricate woodwork officially classed as a C-19 design.[4] The track connection with the GER was severed in 1907 and Bishopsgate was renamed Liverpool Street in 1909 shortly before a new lever frame of 20 levers was installed enabling bay platform 3 to be brought into regular use during 1910. The signal cabin gained its first prefix identification of G by 1912.[3]
London Transport[edit | edit source]
On 21 February 1954, the signal cabin was re-lettered to prefix OD and an electrically interlocked Westinghouse ‘B-style’ miniature lever frame replaced the existing one within the confines of the existing building. From 12 December of the same year, signal cabins at Liverpool Street and Barbican (prefix OG) were converted to remote operation as Interlocking Machine Rooms (IMR) with control transferring to the cabin at Farringdon (prefix OH).[3] The idea behind this was to concentrate signalling control where track layouts were now small enough to make remote operation by push button desks by a single signaller feasible. Prior to the 1950’s, the railway between Farringdon, Barbican and Liverpool Street had an extensive web of goods sidings and spurs necessitating local signal cabins. Whilst some of these were still operational during the 50's and 60's, they were shadows of past operating needs and goods traffic would continue to decline into obsolescence by the 1970’s.
In January 1981, bay platform 3, was taken out of use to provide office space for British Rail during the rebuilding of the mainline station.[5] Once the offices were dismantled, the decision was taken not to re-commission the platform and the track layout was subsequently rationalised. This left a shunt signal, a trailing crossover and four signals in the control area of Liverpool Street IMR, the final layout that lasted until closure.
Farringdon signal cabin was converted to an IMR in 1999 with control being absorbed into Baker Street Service Control Centre. The Liverpool Street IMR area subsequently passed control to Baker Street SCC on 25 March 2001.[3] The decisions to abolish platform 3 and not re-align the remaining crossover meant that unusually for the Underground, the points are located within the station platforms. This rendered them unusable to trains in passenger service that were longer than a 6-car train of C stock bar extreme emergencies.
Four Lines Modernisation[edit | edit source]
The replacement of the C stock with longer S stock trains from 2014 further reduced the usability of the crossover now only being able to be traversed in the reverse position by trains that were out of service. Despite the historic peculiarities of this crossover, it was fully incorporated into Communications Based Control (CBTC) as part of the Four Lines Modernisation (4LM) re-signalling programme. Transition from legacy signalling to CBTC on the Sub-Surface Railway was split into 14 Signal Migration Areas (SMA). Liverpool Street fell into SMA 3 concerning the railway between Euston Square, Monument and Stepney Green. After testing and a series of aborted go-live dates, Liverpool Street IMR closed after traffic in the early hours of 6 March 2021, bringing to a close 146 years as an operationally active building. SMA 3 subsequently entered revenue earning service the following day.
Liverpool Street IMR gained Grade II listing by Historic England in 2013 and as such is protected from unsympathetic redevelopment or demolition.[4]
References[edit | edit source]
- ↑ Bownes, David; Green, Oliver; Mullins, Sam (2012). Underground : How the Tube Shaped London. Allen Lane. ISBN 978-1-846-14462-2.
- ↑ Smith, Denis (2001). London and the Thames Valley. Civil Engineering Heritage. Thomas Telford. ISBN 0727728768.
- ↑ 3.0 3.1 3.2 3.3 Horne, Mike (2020). Inventory of Signal Cabins and Other Interlockings: London Transport Railway
- ↑ 4.0 4.1 Historic England. "SIGNAL BOX AT LIVERPOOL STREET LONDON UNDERGROUND (1574542)". PastScape
- ↑ "More on Liverpool Street". Underground News. Vol. 732. London Underground Railway Society. December 2022. p. 726.