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Four Lines Modernisation (shortened to 4LM) is a wholesale re-signalling programme encompassing London Underground’s Circle, District, Hammersmith & City and Metropolitan lines. Combined, these lines make up over 40% of the network and cover the oldest sections of urban rapid transit in the world dating back to 1863.[1]

Origins

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The Circle, District, Hammersmith & City and Metropolitan lines, known as the sub-surface lines, have a complex intertwined history stretching from the heart of the City of London to rural backwaters with many historical oddities ranging from timetables to rolling stock and infrastructure. The introduction of the S7 and S8 stock constructed by Bombardier between 2009 and 2017 was the first successful attempt since the 1950’s to introduce a standardized design of rolling stock for these closely interlinked lines all of which share significant portions of their route with one another with numerous flat junctions posing a significant obstacle to increasing service frequency even with new trains.

Following on from this, in 2011, London Underground awarded Bombardier Transportation the contract for a signalling upgrade programme initially called Sub-Surface Upgrade Programme (SSUP) with the aim of providing the sub-surface lines with Automatic Train Control (ATC) to increase capacity making the best use of the 192 fleet of new trains, at the time the largest single rolling stock order for a train operator in the United Kingdom.[2]

However, by December 2013, it was becoming apparent that Bombardier’s inexperience in this field was making delivery of the project increasingly fraught and London Underground subsequently terminated the contract through an £85 million break off settlement. The collapse of this programme prompted an uproar at the time leading to a highly critical report published by London Assembly citing inherent weaknesses in the procurement process. The culmination of this saga led to Thales being selected as the replacement for the now renamed Four Lines Modernisation in the Summer of 2015 with a revised final completion date of 2023, five years later than originally planned.[3]

Scope

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Whilst centralised control centres first pioneered by London Transport in the 1960’s on the Victoria line had attempted to concentrate signal control into larger areas[4], large portions of these lines are still controlled by signal cabins covering small geographic areas through push button or mechanical lever frames requiring manual input from signallers as well as regular maintenance for equipment that is now obsolete and increasingly expensive to maintain and repair. As an example of this, Edgware Road signal cabin of 1926 vintage, required over 3600 manual lever movements a day to move trains through an area encompassing just two stations.

Prior to the commencement of 4LM, the sub-surface lines had existing control centres at Baker Street and Earl’s Court as well as signal cabins at Amersham, Barking, Edgware Road, Hammersmith, Harrow-on-the-Hill, Rayners Lane, Rickmansworth, Whitechapel and Upminster. All existing London Underground operated control centres and signal cabins will be progressively closed and transfer to Hammersmith Service Control Centre.[5]

The sub-surface lines have been split into Signal Migration Areas (SMA’s) numbered 0.5 to 14 by which a variant of Automatic Train Control (ATC) referred to by Thales as Communications Based Train Control (CBTC) will replace fixed block signalling dispensing with most lineside signals in the process.[6]

Four Lines Modernisation Signal Migration Areas[7]
SMA Location Line Commissioning Previous area of control Notes
0.5 Hammersmith - Latimer Road Circle and Hammersmith & City 17 March 2019 Hammersmith signal cabin Split from SMA 1
1 Latimer Road - Paddington Circle and Hammersmith & City 1 September 2019 N/A - Automatic signalling in operation Commissioned with

SMA 2

2 Paddington/Finchley Road - Euston Sqaure Circle, Hammersmith and City,

District and Metropolitan

1 September 2019 Edgware Road signal cabin

Baker Street Signalling Control Centre

Commissioned with

SMA 1

3 Euston Square -

Stepney Green/Monument

Circle, Hammersmith and City and Metropolitan 7 March 2021 Baker Street Signalling Control Centre

Earl's Court Signalling Control Centre

4 Monument - Sloane Sqaure Circle and District 2 May 2021 Whitechapel signal cabin

Earl's Court Signalling Control Centre

5 Sloane Square - Paddington/Olympia/

Barons Court/Fulham Broadway

Circle and District lines 11 July 2021 Earl's Court Signalling Control Centre
6 Stepney Green - Becontree District and Hammersmith & City 10 October 2021 Barking signal cabin
7 Becontree - Upminster District 5 December 2021 Upminster signal cabin
8 Finchley Road - Preston Road Metropolitan 6 March 2022 Baker Street Signalling Control Centre
9 Preston Road -

West Harrow/Moor Park

Metropolitan 4 August 2022 Harrow-on-the-Hill signal cabin
10 Barons Court - Richmond/Chiswick Park District N/A Earl's Court Signalling Control Centre

Richmond signal box (Network Rail)

Deferred indefinitely

as of 2020

11 Chiswick Park -

Ealing Broadway

District N/A Earl's Court Signalling Control Centre Deferred indefinitely

as of 2020

12 Fulham Broadway - Wimbledon District N/A Earl's Court Signalling Control Centre

Wimbledon Signalling Centre (Network Rail)

Deferred indefinitely

as of 2020

13 Moor Park - Watford/Amersham/Chesham Metropolitan 5 February 2023 Rickmansworth signal cabin

Amersham signal cabin

14 West Harrow - Uxbridge Metropolitan April 2023 Rayners Lane signal cabin


Conventional colour light signalling will be retained over the following sections where non-compatible rolling stock shares track with the sub-surface lines:

Harrow-on-the-Hill – Moor Park (Main Lines only): Metropolitan line shared with Chiltern Railways on London Underground infrastructure but using Network Rail-style fixed block signalling

Gunnersbury – Richmond: District line shared with London Overground operating over Network Rail infrastructure

Acton TownEaling Common: District line shared with the Piccadilly line using legacy fixed block signalling

East Putney – Wimbledon: District line shared with South Western Railway using Network Rail controlled signalling infrastructure

Progression

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On 17 March 2019, SMA 0.5 was pressed into revenue earning service closing Hammersmith OZ signal cabin which at the time of closure was over 60 years old. This marked the beginning of the rolling programme of signal migration across the sub-surface lines aimed at reducing risk and disruption through weekend closures by compartmentalising parts of the railway to be worked on.[8][9]

On 1 September 2019, both SMA 1 and SMA 2 were brought into use closing the then 93-year-old Edgware Road OP signal cabin reputed to be the oldest signal cabin still in use on a rapid transit system anywhere in the world. This was also the first time that CBTC was being used by all four sub-surface lines.[10]

The rollout of SMA 2 in particular over the Metropolitan line between Finchley Road and Euston Square was the subject of intense scrutiny over the high rate of cancellations caused by the repeated pushing back of the roll out date requiring a significant pool of drivers to undertake refresher courses for working with CBTC operated trains.[11]

In the wake of the Coronavirus pandemic and subsequent lockdown ordered by the UK Government, in March 2020 all work on Transport for London construction sites and upgrade projects including 4LM were brought to a safe stop.[12] It was announced at the end of June 2020 that works would resume as restrictions eased.[13]

Following a review of Transport for London's finciacies triggered by an emergency bailout package from the UK Government, several projects including those affecting London Underground where placed into review. In August 2020, the scope of Four Lines Modernisation was reduced when SMA's 10, 11 and 12 were removed from the programme. The affected areas on the District line west of Baron's Court and south of Fulham Broadway will retain existing fixed block signalling equipment.

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References

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  1. ^ "Four Lines Modernisation: Making four lines fit for the future". www.macegroup.com. Retrieved 2020-06-14.
  2. ^ 2019-03-20T10:36:23+00:00. "First stage of 'highly complex' London Underground resignalling goes live". Railway Gazette International. Retrieved 2020-06-14.{{cite web}}: CS1 maint: numeric names: authors list (link)
  3. ^ "Transport for London's Signal Failure" (PDF). London Assembly Budget and Performance Commitee.
  4. ^ "Victoria Line renaissance | Rail Engineer". Retrieved 2020-06-14.
  5. ^ "Inventory of Signal Cabins and Other Interlockings" (PDF). London Transport Railways.
  6. ^ "First section of London Underground SSL resignalling goes live". International Railway Journal. 2019-03-20. Retrieved 2020-06-14.
  7. ^ "Four Lines Modernisation Update" (PDF). Programmes and Investment Committee.
  8. ^ "First section of London Underground SSL resignalling goes live". International Railway Journal. 2019-03-20. Retrieved 2020-06-14.
  9. ^ "#TheLastStroke for the Hammersmith and City Railway". MoreToJack. 2019-03-15. Retrieved 2020-06-14.
  10. ^ "This 92-Year-Old Tube Signal Cabin Is Still In Use... But It Won't Make It To 100". Londonist. 2019-05-15. Retrieved 2020-06-14.
  11. ^ "'I'm spending all my time commuting or working'". BBC News. Retrieved 2020-06-14.
  12. ^ Matters, Transport for London | Every Journey. "TfL and Crossrail construction sites to come to Safe Stop". Transport for London. Retrieved 2020-06-14.
  13. ^ Matters, Transport for London | Every Journey. "TfL's construction projects to commence phased restart". Transport for London. Retrieved 2020-06-14.
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