Editing Upminster signal cabin

}}Upminster (prefix FM) is a signal cabin located near the station of the same name on London Underground’s District line as part of the Sub-Surface Railway. In its final years, Upminster ranked amongst the smallest signal cabins on the London Underground network. Opened in 1958, it closed in 2023 as part of the Four Lines Modernisation (4LM) re-signalling programme.

It is not to be confused with the Network Rail Integrated Electronic Control Centre (IECC) overseeing the North London Line and London, Tilbury and Southend routes which is also located at Upminster.  

Whilst the District Railway had been serving Upminster since 1932<ref>[http://www.davros.org/rail/culg/district.html Clive's Underground Line Guides - District line]</ref>, it was through a shared running agreement using infrastructure and stations managed by first by the London Midland & Scottish Railway (LMS) up until 1948 and then by the Eastern region of British Railways (BR). It took until 1969 for majority of the stations and infrastructure between Whitechapel and Upminster to be fully incorporated into London Transport.

The current signal cabin opened on 20 November 1958 equipped with a Westinghouse push button desk. The desk controlled a single Interlocking Machine Room (IMR) equipped with a V-style frame remotely operated by compressed air in response to the signaller setting signals and points via the push button desk. As was the case with all IMR’s, the air supply could be isolated and worked manually in the event of a failure.

The signal cabin itself was timed to be brought into operation in conjunction with Upminster Depot, a stabling and maintenance facility built to compensate for the closure of East Ham Depot. On 13 November 1960 Upminster signal cabin reached its final extent of control with the addition of an Interlocking Machine Room (IMR) at Hornchurch replacing an LMS signal box dating from 1930.<ref>Horne, Mike (2006). ''The District Line''. Harrow, Middlesex: Capital Transport. ISBN <bdi>1-85414-292-5</bdi>. OCLC 85863502.</ref>

The implementation of push button desks by Westinghouse marked the final chapter of development of signal cabin design and operation on the Underground. Modifications to existing signal cabins, many of which contained substantial lever frames would often entail partial or wholesale conversion to push button operation with signal cabins at [[Harrow-on-the-Hill signal cabin|Harrow-on-the-Hill (JB)]] and Rayners Lane (JP) being notable examples.

In 1962, Earl’s Court control room opened absorbing control of majority of the District line west of Aldgate East. The use of programme machines being able to automatically set signals and points based on a preloaded timetable dispensed with the need for signal cabins which previously had been required at most diverging junctions or termini locations such as Upminster. Whilst the signal concentration schemes on the District and Northern lines had been successful, the large capital costs of such schemes coupled with the financial insecurities that London Transport endured through various governmental changes meant that the full scale of this ambition was never realised. As a result, signal cabins remained in large numbers into the 21^st century.

It was the introduction of the S8 and S7 stocks between 2010 and 2015 that was to prove the catalyst for wholesale re-signalling of the SSR. Bombardier, manufacturers of the S stock trains were also contracted to replace the legacy fixed-block signalling with Distance To Go Radio (DTGR), a form of Automatic Train Operation (ATO). The re-signalling was to be known as the Sub-Surface Upgrade Programme (SSUG). However, Bombardier’s inexperience in delivering signalling systems soon started to drag the SSUG behind schedule and faced with mounting costs and delays, London Underground terminated the contract in 2013 at an estimated cost of £900m and a completion date delay of five years.

Thales won the re-tendered contract for SSR re-signalling in 2015 which had been renamed as Four Lines Modernisation (4LM). Thales would introduce Communications Base Train Control (CBTC), a variant of SelTrac ATO. Migration to ATO on the SSR is split into 14 Signal Migration Areas (SMA) of which Upminster lies in SMA 7 concerning the railway between Becontree and Upminster. Following extensive testing, Upminster signal closed on 18 March 2023 upon the commissioning of SMA 7.