Edgware Road signal cabin

Edgware Road
OP
Overview
Opened	10 October 1926
Closed	31 August 2019
Operator	London Underground

Edgware Road (prefix OP) is a signal cabin located within the station of the same name on the Circle, District and Hammersmith & City lines of London Underground’s Sub-Surface Railway. Brought into use on 10 October 1926, it was the oldest operational signal cabin on a rapid transit system globally by the time of its closure on 31 August 2019 as part the Four Lines Modernisation (4LM) re-signalling programme.

Metropolitan Railway

Edgware Road is located on the oldest section of underground metro in the world dating from the opening of the Metropolitan Railway (MR) between Paddington and Farringdon on 10 January 1863. The original MR station at Edgware Road was a two-track station with the original signal box (prefix C) of 30 levers provided. This controlled Praed Street Junction to the west which split the lines of the Great Western Railway towards Hammersmith from those of the Metropolitan heading towards High Street Kensington.  The MR also had a series of locomotive sheds housing the steam locomotives that worked the service in the years before electrification from 1905 onwards.

One of the unintended consequences of the pioneering proliferation of underground railway lines by the MR was the capacity limitations caused by lack of route segregation. The MR had planned to construct relief lines between Edgware Road and Kilburn to relive two track section of railway between Baker Street and Finchley Road, by then a notorious bottle neck with no fewer than four separate service patterns all vying for access. In 1926, Edgware Road station was rebuilt into its current layout of a four-track layout in anticipation of those relief lines with the signal cabin (prefix B, later OP) suitably reequipped with the Westinghouse ‘K style’ frame of 39 electrically interlocked miniature levers that would remain with the cabin for the rest of its operational life. Government legislation regarding the safety standards of locomotive hauled rolling stock would eventually render the MR’s proposed extension economically unfeasible and the plan was subsequently dropped.

London Transport

It would take until 1939 with the New Works Programme enacted by the London Passenger Transport Board (LTPB) to fulfil the ambition of relieving the tracks between Baker Street and Finchley Road in the form of the Bakerloo line. Running in newly constructed Deep Tube tunnels between Baker Street and Finchley Road, the Bakerloo line took over MR services to Stanmore providing the service segregation that had always been absent from the MR’s original plans due to the ad-hoc nature of its expansion.

Whilst the now expanded Edgware Road never saw its intended use come to fruition, it remained a pivotal area of the Sub-Surface Railway with the through services of the Circle and Metropolitan lines, terminating District line services and substantial goods traffic from the Great Western Railway through to Billingsgate market near Farringdon.

Signal Concentration Schemes

Up until the 1960’s, the tried and accepted way of controlling signals and points was by installing signal cabins and lever frames wherever manual control of a route was needed for example at terminal stations or diverging junctions. Whilst experiments by Westinghouse Brake and Signalling company on the Piccadilly line in the 1940’s with automatic junction working had yielded desirable results, signal concentration was someway off, and cabins commissioned into the late 1950’s remained small in terms of geographic area covered.

It was the pioneering advancements in technology that led to the opening of control rooms at Earl’s Court (1965) and Coburg Street (1969) that proved that the concentrating of signalling control of entire lines into a single facility was a tangible prospect. In both cases, the huge geographic coverage of these control rooms was made possible by push button panels replacing lever frames and the partial automation of route setting by means of programme machines routing trains according to a pre-loaded timetable. Signallers would be able to intervene if trains were running out of kilter with the timetable via desks of push button panels to manually select routes and interpose timetable commands.

In the late 1980’s, Baker Street control room began to absorb signalling control of the Jubilee, Metropolitan and northern half of the Circle line starting with the Jubilee line in 1986. It had originally been envisaged that Baker Street would eventually replace Edgware Road signal cabin as well take over signalling for the entirety of the Metropolitan line from its remaining signal cabins. However, financial constraints brought a premature end to this programme and as a result, the enabling works that put Edgware Road on the display panel at Baker Street control room would never be brought into use.

Four Lines Modernisation (4LM)

In 2011, Bombardier were awarded the contract for re-signalling the entirety of the Sub-Surface Railway as part of a project called Sub-Surface Upgrade Programme (SSUG) utilising Distance-To-Go-Radio (DTGR) similar to that used on the Victoria line. However, Bombardiers relative inexperience in this field quickly started to pull SSUG behind schedule and London Underground subsequently terminated the contract in 2013. In 2015, Thales won the re-tendered contract for Sub-Surface Railway re-signalling using Communication Based Train Control (CBTC), a variant of SelTrac. As a result of the re-tendering process, the target date of completion for the project slipped a minimum of five years and an extra £900m.

During 2016, Edgware Road signal cabin reached 90 years in commission, an unprecedented achievement for signalling on a rapid transit system. In recognition of this historic milestone, the Railway Heritage Designation Advisory Board (RHDAB) designated Edgware Road signal cabin an item of national historic interest. After closure, the cabin would be preserved with the ambition of it becoming accessible to the general public.

Following intensive testing and a series of aborted go-live dates, 4LM began a rolling programme of signalling migration from fixed-block signalling to TBTC starting in March 2019 with SMA 0.5 between Hammersmith (Circle and Hammersmith & City lines) and Latimer Road. Edgware Road signal cabin subsequently closed after close of traffic in the early hours of 31 August 2019 with the commissioning of SMA 2 (Paddington and Finchley Road to Euston Square) after almost 93 years of continuous operation.

References

Citations

1. Edwards, Dennis; Pigram, Ron (1988). The Golden Years of the Metropolitan Railway and the Metro-land Dream. Bloomsbury. p. 32. ISBN 1-870630-11-4.
2. Simpson, Bill (2003). A History of the Metropolitan Railway. Vol 1. Lamplight Publications. ISBN 1-899246-07-X.
3. Jackson, Alan (1986). London's Metropolitan Railway. David & Charles. ISBN 0-7153-8839-8.
4. Rose, Douglas (1999) [1980]. The London Underground, A Diagrammatic History (7th ed.). Douglas Rose/Capital Transport. ISBN 1-85414-219-4.
5. "London Underground and Bombardier abandon Tube signalling contract". International Railway Journal. 3 January 2014.
6. "Oldest LU signal cabin earmarked for preservation". Rail Express Magazine. 31 October 2016.
7. "First stage of ‘highly complex’ London Underground resignalling goes live". Railway Gazette. 20 March 2019.
8. "TP Blog: End of an era at Edgware Road". CIHT. 11 September 2019.