Downtown MRT line

At the official opening of the Dover MRT station on 23 October 2001, then-Minister for Communications and Information Technology Yeo Cheow Tong announced three MRT lines, two of which―the Bukit Timah Line and the northern part of the Eastern Region Line―form today's DTL. The Bukit Timah Line aimed to alleviate the traffic problems along the Bukit Timah and Dunearn Road corridor, and provide a direct link to the city area for residents in Choa Chu Kang and Bukit Panjang. The proposed Eastern Region Line, slated to be a loop in the eastern regions, aimed to relieve the passenger load on the often-congested East West line and benefiting those living in Tampines, Bedok and Marine Parade.[9]^:16―17[10][11]

On 14 June 2005, the Land Transport Authority announced the Downtown Extension (renamed to "Downtown Line Stage 1") to serve the New Downtown at Marina Bay area, where an integrated resort (Marina Bay Sands) and Singapore's second botanical garden (Gardens by the Bay) were to be located. The 3.4-kilometre (2.1 mi) fully underground line was estimated to cost S$1.4 billion.[12] On 27 April 2007, then Transport Minister Raymond Lim announced that the newly christened Downtown Line would be built in three stages stretching 40 kilometres (25 mi) with 33 stations.[13][14][15][16]

The construction of DTL tunnels near Clarke Quay. The diversion of the Singapore River for construction works for the tunnels between the Chinatown and Fort Canning stations was considered an engineering feat at the time.[17][18][19]

A separate entrance for the DTL platforms for Tampines MRT station, which is not directly connected to the EWL platforms of the station.

The line was built in 3 stages: Stage 1 of the Downtown line, stretching 4.3-kilometre (2.7 mi), started construction in January 2008 at Chinatown station[9]^:30, where platform provisions were built to facilitate an interchange station during the construction of the North East line. It began service on 22 December 2013,[20] with its official inauguration made on the day before by Prime Minister Lee Hsien Loong.[21]

Stage 2e, first conceptualized and announced as the Bukit Timah line on 23 October 2001, is 16.6 kilometres (10.3 mi) long with 12 stations connecting Bukit Panjang and Rochor stations, including four interchange stations. Construction for Stage 2 began on 3 July 2009 with a groundbreaking ceremony at Beauty World station.[22][23][24][25]

Stage 3 goes from Chinatown to Expo. The station locations and finalised route were unveiled on 20 August 2010.[26][27] Stage 3 of the Downtown line is 21 kilometres (13 mi) long and serve 16 stations.[1][28] The route opened on 21 October 2017,[29] with free travel for all DTL stations on the first two days of the line completion.[30][31]

The line, with an estimated cost of S$12 billion, was considered the government's most ambitious rail project. The cost exceeded those of the Circle Line (at $6.7 billion) and the North East Line (at $4.6 billion). Final costs of building the line may reach an estimated about S$20.7 billion, up more than 70% from the initial estimation, due to sharp rises in construction costs and a number of changes in plans.[32][9]^:19.

In October 2014, it was announced that Stage 2's opening would be pushed back to the first quarter of 2016. This was because one of the main contractors for the DTL2, Alpine Bau (which was building King Albert Park, Sixth Avenue and Tan Kah Kee), went bankrupt in mid-2013.[33] On 28 June 2015, Transport Minister Lui Tuck Yew announced that the delay was "completely resolved" by the authorities and Stage 2's opening date was brought forward to 27 December 2015.[34][35] The DTL 3 started operations on 21 October 2017, officially opened by Transport Minister Khaw Boon Wan.[36][37]

To serve the line, the Gali Batu Depot was opened in December 2015 to stable 42 trains. It is situated at part of the former Kwong Hou Sua Teochew Cemetery off Woodlands Road.[38] Also in February that year, the Land Transport Authority announced that the capacity of the depot will be expanded to stable 81 trains by 2019.[39]

On 17 January 2013, plans for a southern extension which will run from Expo through the East Coast area, interchanging with the Thomson–East Coast line were announced for completion by 2024.[40][41] On 31 May 2017, LTA announced that Stage 3 of the Downtown line will commence operations on 21 October 2017.[42]

DTL3e was announced on 15 August 2014, in conjunction with the announcement of the Thomson–East Coast line.[43] Two stations, Xilin MRT station and Sungei Bedok MRT station, will be added to the Downtown Line, with Sungei Bedok as an interchange station with the Thomson–East Coast line. It will lengthen the line by 2.2 km (1.4 mi).[43] Expected t be completed in 2024, Stage 3e will join the current East West and future Thomson–East Coast lines that runs through Marine Parade.[44]

On 7 March 2019, Hume station was announced to be opened by 2025 to better serve Hillview residents.[5] An additional extension to the Downtown Line to Sungei Kadut station from Bukit Panjang station was announced on 25 May 2019 by the LTA. The extension is set to cut down travel time to the downtown area by up to 30 minutes for those living in the northwestern area of Singapore. The extension is expected to be completed by the mid-2030s. A study will also be conducted to determine the stops to be added between the Sungei Kadut and the existing Bukit Panjang stations.[6]

A malfunction in the platform screen doors at Botanic Gardens resulted in trains bypassing the station and a seven-hour disruption on 3 May 2017. Downtown line operator SBS Transit said that the doors malfunctioned at 5.45am due to a signalling-related fault, and could not open automatically. The fault was rectified at 12.54pm and the platform reopened for passenger service, with the affected door remaining closed for repairs.[45]

Geographically accurate map of the Downtown MRT line.

The Downtown line generally goes in an east-west direction from Bukit Panjang in the northwestern side of Singapore, through the downtown area of Singapore, to Tampines and the Singapore Expo at the east. It is 41.9 kilometres (26.0 mi) long and is entirely underground. Before Bukit Panjang station, there exists a brief northwards extension to the line's depot Gali Batu Depot. The line currently begins at Bukit Panjang station[46] and then goes in the southeast direction, running parallel to Upper Bukit Timah Road and along the Bukit Timah Canal through Bukit Timah.[47] The line then enters the central area, passing through Little India station[48] before reaching the Central Business District via Bugis station.[49] The Downtown line runs parallel to the Circle line at the Promenade[50] and Bayfront stations.[51] Passing through the Downtown Core, the line interchanges with the North East line at Chinatown station.

After Chinatown station, the line goes in a northeast direction and under the Singapore River.[52] Between the Bencoolen and Jalan Besar stations, the line intersects itself, the first MRT line to do so.[53] After Geylang Bahru station, the line continues in a general eastwards direction,[54] through the industrial areas of Kampong Ubi and Kaki Bukit (briefly paralleling Ubi Avenue 2 and Kaki Bukit Avenue 1),[55] before continuing towards the Tampines Regional Centre and goes southwards, ending at Changi Business Park.[56] The DTL3 extension (DTL3e) from Expo station will extend the line further towards the Thomson–East Coast line at Sungei Bedok station.[57][58]