The Thomson–East Coast line (TEL) is a medium-capacity Mass Rapid Transit (MRT) line in Singapore that is currently under construction, being the sixth line to be built. The line was announced on 15 August 2014 by the Land Transport Authority as the merger of the Thomson Line (TSL) and the Eastern Region line (ERL). The stretch from Woodlands North to Gardens by the Bay costs S$18 billion. The line will open in five stages from 2019 onwards, and interchanges with all existing lines. When the line fully opens, it is expected to serve about 500,000 commuters daily in the initial years, rising to one million commuters daily in the long term. It will be the fourth MRT line to be operated by SMRT, after the North South line, East West line and the Circle line and also the fourth to be completely automated and driverless. This line is coloured brown on the rail map.
The fully underground line is 43 km (27 mi) long and consists of 31 stations, and will be among the world's longest driverless rapid transit lines. It will run through a combined north-south and east-west corridor, starting in the north at Woodlands town, then passing through the towns of Ang Mo Kio and Bishan, after that heading south to the residential estates of Thomson and Stevens, the shopping districts of Orchard Road and Marina Bay, then running eastwards along the east coast through Kallang, Marine Parade and Bedok South, before ending at Upper East Coast. Its depots are located at Mandai, south of Woodlands, and near the south-eastern terminus of the line at Tanah Merah. By 31 December 2024, the planned Rapid Transit System (RTS) Link will interchange the line's Woodlands North terminus, allowing it to extend to Malaysia. The Land Transport Authority announced on 11 August 2017 that the Thomson–East Coast line will be the first cashless MRT line.
The Thomson Line was first announced on 25 January 2008. Several architectural and engineering consultancy packages were released in 2010 which indicated an increase in the number of stations from 18 in the initial announcement to the current 22 and length of the line from 27 km to 30 km.
On 16 June 2011, the Land Transport Authority announced the location of the depot for the line, due to begin construction at the end of 2012. It also announced Woodlands as an interchange with the existing North South line and an additional station located near to Republic Polytechnic. In addition, the northern terminus will also house the Johor Bahru RTS link.
On 29 August 2012, it was announced the Thomson Line will be ready from 2019 onwards instead of the indicative timeline of 2018 announced in the Land Transport Masterplan.
Construction of the Thomson Line began in January 2014.
The Eastern Region Line was first officially announced on 18 October 2001. In its preliminary plans, Eastern Region Line was to have been a 40 kilometre rectangular loop that would complement the existing East West line and enhance inter- and intra-town travelling in the eastern region. It would have looped around the Jalan Besar and East Coast areas, intersecting the Circle line and other lines along the way, benefiting residents in Tampines, Bedok, Marine Parade, MacPherson and Kaki Bukit. However, the northern part of the loop which includes Jalan Besar, Tampines, MacPherson, Bedok North and Kaki Bukit is now part of the Downtown Line Stage 3. The ERL is now planned to closely follow the southern stretch of the originally announced plan.
On 11 July 2012, a speech by Mrs Josephine Teo, Minister of State, Ministry of Finance and Ministry of Transport, at Downtown Line 3 (DTL3) Tunelling Works Ceremony, announced that the Land Transport Authority (LTA) are starting architectural and engineering consultancy studies for the Eastern Region Line, which will eventually connect to the Thomson line.
On 29 May 2013, Land Transport Authority director of rail services, Melvyn Thong said at the Modern Railways conference, there are plans to extend ERL and link to the future Singapore Changi Airport's Terminal 4 which is set to be ready by 2017 but on 1 June 2013, LTA clarified that ERL will not provide an MRT link to the planned Terminal 4, but instead, on 30 August 2013, Minister of State for Transport Josephine Teo unveiled plans that it will be linked to the future planned Singapore Changi Airport's Terminal 5, a mega terminal, which will be the largest terminal in Singapore upon completion around the mid 2020s.
On 15 August 2014, it was announced that the Eastern Region line would be merged with the Thomson line to form the Thomson–East Coast line, extending the project to five stages, with nine more stations. This is more than the number of stations originally planned on the line.
On 21 July 2016, the groundbreaking ceremony for the East Coast stretch took place at Marine Parade. All the working station names, including Xilin on the Downtown Line extension, were confirmed as the final names except for Amber station which was changed to Tanjong Katong. The authorities are also considering extending the TEL to all terminals at Changi Airport, including the upcoming Terminals 4 and 5, announced Transport Minister Khaw Boon Wan. 
On 20 January 2017, it was announced that studies are ongoing for the possibility of extending the TEL from Sungei Bedok to serve the future Changi Airport Terminal 5, further extending to Changi Airport Terminal 1, 2 and 3, and to Changi Village. This way, commuters in the future can enjoy a seamless ride on the TEL from the city centre to any of the terminals in Changi Airport without having to change lines.
Thomson-East Coast MRT Line
|Station Number||Station Name||Interchange/Notes|
|Stage 1 (under construction, to be ready by 2019)|
|Woodlands||Interchange with the North South Line|
|Stage 2 (under construction, to be ready by 2020)|
|Caldecott||Interchange with the Circle Line|
|Stage 3 (under construction, to be ready by 2021)|
|Stevens||Interchange with the Downtown Line|
|Orchard||Interchange with the North South Line|
|Outram Park||Interchange with the East West Line and the North East Line|
|Marina Bay||Interchange with the North South Line and the Circle Line extension|
|Gardens by the Bay|
|Stage 4 (under construction, to be ready by 2023)|
|Stage 5 (under construction, to be ready by 2024)|
|Sungei Bedok||Interchange with the Downtown Line|
The Thomson–East Coast line is equipped with Alstom Urbalis 400 Communications-based train control (CBTC) moving block signalling system with Automatic train control (ATC) under Automatic train operation (ATO) GoA 4 (UTO). The subsystems consist of Automatic train protection (ATP) to govern train speed, Iconis Automatic Train Supervision (ATS) to track and schedule trains and Smartlock Computer-based interlocking (CBI) system that prevents incorrect signal and track points to be set.