Initial developments The first segment of what would become the East–West Line, between
City Hall and
Outram Park stations, was opened on 12 December 1987 as part of the North–South Line and Phase 1 of the initial system. and to
Lakeside on 5 November 1988. The eastern extension to
Tanah Merah station opened on 4 November 1989, which also marked the start of independent operations as the East–West Line. The line extension to
Pasir Ris station was opened ahead of schedule on 16 December 1989 with a sneak preview beforehand.
Boon Lay station opened on 6 July 1990, marking the completion of the initial MRT system.
Subsequent developments Dover station Construction on a new
infill station located between
Buona Vista station and
Clementi station, namely
Dover station, began in June 1998. It is the first station in the MRT network to be built as an infill station. The building of the station was met with reservations by some members of the public over the small area it serviced and there were criticisms over the spending of "taxpayers' money" chiefly for use only by students of one educational institution. Despite some opposition, the
Land Transport Authority proceeded with the construction to serve commuters along Singapore Polytechnic with Dover housing estate. The station opened on 18 October 2001. Prior to opening, test runs were conducted from 13 to 17 October 2001, where the trains stopped at the station but did not open their doors.
Tanah Merah to Airport extension line The idea of extending the Mass Rapid Transit system to
Changi Airport was reconsidered when Terminal 3 of the airport was being built. Earlier plans had long been made for a new line branching off from the existing East–West Line at
Tanah Merah, with some conceptual plans showing a tentative route alignment up to the airport along Airport Boulevard, continuing beyond the airport to Changi Point, before turning southwest back towards the city along the eastern coasts. The plans were finally announced by then
Deputy Prime Minister Lee Hsien Loong on 15 November 1996. However, the new route alignment showed a deviation from previous plans, where the final plan involved in building only the first two stations of
Expo, and Changi Airport, the latter being the underground station built between Terminal 2 and
Terminal 3. The alignment of the station at the airport also switched perpendicularly to an east–west direction, such that the station leads to two of the terminals directly from either end of the station. The station's designs were unveiled on 10 February 1998 with construction starting on 29 January 1999. Expo and Changi Airport were opened on 10 January 2001 and 8 February 2002 respectively and operates under a shuttle service. Prior to 22 July 2003, train services from Boon Lay commences after the opening, but were later reverted to shuttle services due to low patronage. On 25 May 2019, it was announced that the Changi Airport Extension would be converted to become part of Thomson–East Coast Line Extension (TELe) by 2040.
Boon Lay and Tuas extension The Boon Lay extension was first announced by the LTA on 29 December 2004, set to serve residents from the Jurong West Town area and those working in the Jurong Industrial Estate. The two stations,
Pioneer and
Joo Koon stations, officially opened on 28 February 2009. On 11 January 2011, the Tuas West extension, an extension of the East–West Line from
Joo Koon to
Tuas Link was announced. The extension has a span of , which spans a twin-tracked MRT viaduct, four above-ground stations and a depot to provide stabling and maintenance facilities for the additional trains that will be bought for the extension and to cater for future expansion of the line. The viaduct is integrated with part of a road viaduct along Pioneer Road, which will increase the road capacity to cope with anticipated increase in traffic. The stations are
Gul Circle,
Tuas Crescent,
Tuas West Road, and
Tuas Link. On 4 May 2012, the
Land Transport Authority marked the start of construction of the Tuas West extension with a groundbreaking ceremony at the site of the future Tuas Link station. The extension began service on 18 June 2017. During initial stages after opening, the westbound trains will alternate their terminus between
Joo Koon and
Tuas Link, where for every two trains, one train will terminate at the former, while the other train will terminate at the latter. In 2025, the LTA announced that 40 stations on the North–South and East–West lines will gain
public artworks, as part of expansion of the Art in Transit programme.
Additional platform at Tanah Merah station On 25 August 2014, the
Land Transport Authority announced that a new island platform will be constructed at
Tanah Merah, enabling faster travel and shorter waiting times for commuters heading towards
Expo and Changi Airport on the Changi Airport branch line of the East–West Line. On 26 October 2016, the
Land Transport Authority awarded the civil contract to Lum Chang Building Contractors Pte. Ltd. to build a new platform at Tanah Merah and viaducts for a contract sum of S$325 million. In addition to the new platform, the existing East–West Line tracks will be extended to connect the line to the new four-in-one
East Coast Integrated Depot at Changi. When completed in 2025, it will be the second station to have three island platforms side-by-side after
Jurong East.
Half-height platform screen door installations There were calls for platform screen doors (PSDs) to be installed at above-ground stations after several incidents in which passengers were killed or seriously injured by oncoming trains when they fell onto the railway tracks at above-ground stations. Underground stations already featured the doors since 1987. The authorities initially rejected the proposal by casting doubts over functionality and concerns about the high installation costs, but made an about-turn later with the government announcing plans to install
half-height platform screen doors on the elevated stations by 2012 on 25 January 2008, citing lower costs due to it becoming a more common feature worldwide. Contract C1320 for the design and installation of half-height platform screen doors was awarded to Singapore Technologies Electronics Limited in September 2008 for . They were first installed at
Jurong East,
Pasir Ris, and
Yishun stations in 2009 as
trial runs. On 31 August 2011, the LTA announced completion of the installation of PSDs along the East–West Line, with
Expo being the last station on the line to receive the PSDs. Installation of PSDs across both the
North–South and East–West lines (NSEWL) were completed on 14 March 2012, 3 months ahead of schedule. ==Improvement works==