Editing District line (section)

== Four Lines Modernisation (4LM) ==
{{See also|Four Lines Modernisation}}

It was planned that a new signalling system would be used first on the sub-surface lines from the end of 2016,<ref name="MR3">{{cite news|last=Abbott|first=James|date=January 2013|title=Sub-surface renewal|pages=38–41|work=Modern Railways}}</ref> but signalling contractor Bombardier was released from its contract by agreement in December 2013 amid heavy criticism of the procurement process<ref>{{Cite web|date=3 January 2014|title=London Underground and Bombardier abandon Tube signalling contract|url=https://www.railjournal.com/financial/london-underground-and-bombardier-abandon-tube-signalling-contract/|access-date=2 June 2020|website=International Railway Journal|language=en}}</ref> and London Underground subsequently awarded the contract for the project to [[Thales Group|Thales]] in August 2015.<ref>{{Cite web|date=13 October 2017|title=London Underground resignalling reaches milestone|url=https://www.railjournal.com/signalling/london-underground-resignalling-reaches-milestone/|access-date=2 June 2020|website=International Railway Journal|language=en}}</ref>

With the introduction of S7 Stock, the track, electrical supply, and signalling systems are being upgraded in a programme planned to increase peak-hour capacity on the line by 27 per cent by the end of 2023.<ref name="MR3" /><ref name="TfL-upgrade2">{{cite web|date=February 2011|title=Our Upgrade Plan|url=http://www.tfl.gov.uk/assets/downloads/corporate/our-upgrade-plan-london-underground-february-2011.pdf|url-status=dead|archive-url=https://web.archive.org/web/20120817225410/http://www.tfl.gov.uk/assets/downloads/corporate/our-upgrade-plan-london-underground-february-2011.pdf|archive-date=17 August 2012|access-date=7 December 2012|publisher=Transport for London}}</ref><ref>{{Cite web |title=Four Lines Modernisation|url=https://www.tfl.gov.uk/travel-information/improvements-and-projects/four-lines-modernisation|access-date=2 June 2020|website=Transport for London|language=en-GB}}</ref> A single control room for the sub-surface railway opened at Hammersmith on 6 May 2018, and [[Communications-based train control|Communications Based Train Control (CBTC)]] provided by Thales will progressively replace 'fixed block' signalling equipment dating back to the 1940s.<ref name="MR3" /><ref name="MR22">{{cite news|last=Stewart|first=Rob|date=January 2013|title=Cityflo 650 to control the SSR|pages=42–43|work=Modern Railways}}</ref>

The rollout of CBTC has been split into sections, each known as a Signal Migration Area (SMA), and are located on the line as follows:<ref>{{Cite journal|date=October 2020|title=Underground News|journal=London Underground Railway Society|volume=706|pages=572}}</ref>

{| class="wikitable sortable"
|+ style="text-align: left;" | District line Signal Migration Areas
!data-sort-type="number"|{{Abbr|SMA|Signal Migration Area}}{{efn-lr|SMAs 0.5, 1, 8–9 and 13–14 concerns parts of the Circle, Hammersmith & City, and Metropolitan lines.}}
!from
!class="unsortable"|to
!status
!data-sort-type="isoDate"|date
|-
|2
|Paddington
|Edgware Road
|commissioned
|data-sort-value="2019-09" | September 2019
|-
|3
|Monument
|Stepney Green
|completed
|data-sort-value="2020-07" | July 2020
|-
|4
|Monument
|Sloane Square
|completed
|data-sort-value="2020-08" | August 2020
|-
|5
|Sloane Square
|{{plainlist|
* Olympia
* Barons Court
* Fulham Broadway
* Paddington{{efn-lr|SMA 5 from Sloane Square to Paddington includes the District line from Sloane Square to Earl's Court, and from Earl's Court to Paddington.}}
}}
|completed
|data-sort-value="2022" | March 2022
|-
|6
|Stepney Green
|Becontree
|completed 
|data-sort-value="2022" | January 2023
|-
|7
|Becontree
|Upminster
|completed
|data-sort-value="2023" | March 2023
|-
|10
|Barons Court
|{{plainlist|
* Stamford Brook
}}
|planned
|data-sort-value="9999" | TBD
|-
|11
|Stamford Brook
|Richmond
|deferred
|data-sort-value="9999" | until further notice
|-
|12
|Fulham Broadway
|East Putney 
|planned
|data-sort-value="9999" | TBD 
|}
{{notelist-lr}}