Circle MRT line

The Circle Line dates back to 1989, when then Minister for Communications and Information, Yeo Ning Hong stated that such a system would be "feasible when the population reaches four million", noting the slow population growth and demand.[3]

Feasibility studies for the proposed line commenced on 11 October 1994. The line, then named the Marina Line, was announced on 12 June 1998, as a 12-station underground line (upgraded from LRT to a 3-car MRT line), starting from Chinatown and Dhoby Ghaut via the National Stadium to either Kallang or Paya Lebar stations.[4] However, the Chinatown leg was later removed and the line was reduced to 6 stations up to Stadium station. A part of the removed leg later became part of the Downtown line.[5] On the other hand, a further extension towards Upper Paya Lebar was announced on 28 April 2001.[6] The Marina Line was also merged with a planned LRT line that goes from Paya Lebar to Buona Vista via Serangoon and Bishan to form Circle Line Stage 3 on 20 January 2003,[7] and subsequently Circle Line Stage 4 and 5 on 12 December 2003 when Stage 4 was extended from Buona Vista to World Trade Centre to close up the link and to provide connectivity from the west to Sentosa, becoming the Circle Line.[8][9] On 8 August 2001, SMRT won the bid and was appointed the operator of the Circle Line.[10] Names for the stations for the first three stages of the Circle line were finalised on July 2005 after the Land Transport Authority (LTA) conducted a public consultation exercise on the naming of stations.[11][12] In November 2005, the names of the stations in Stages 4 and 5 were finalised.[13][14][15]

The construction of Bishan station.

Construction started on 13 March 2002 for Stage 1, 5 September 2002 for Stage 2, May 2003 for Stage 3, and January 2005 for Stages 4 and 5. Initially planned to be opened in stages from 2006 to 2010, at an estimated cost of S$6.7 billion, the Nicoll Highway collapse delayed the opening of the first stage to 2009. When the line fully opened on 8 October 2011, the cost of construction had risen to nearly S$10 billion.[16][17] Due to the collapse, the station was relocated to a new site two-thirds the size of the original 100 metres (330 ft) away.[18] Three stations on the Circle Line were initially designed as 'shell stations', but the decision was made to open two of them, Caldecott and Haw Par Villa (previously Thomson and West Coast respectively), leaving Bukit Brown as the only unopened station on the line.[16]

The first section of the line, Stage 3, a 5 kilometres (3.1 mi) five-station segment stretching from Bartley to Marymount, opened on 28 May 2009.[19][20] Initial ridership on this section was lower than estimated, at 32,000 passengers per day (ppd) instead of the estimated 55,000 ppd.[21] Tunneling works for the entire line were completed on 17 August 2009.[22] Stages 1 and 2 started operations on 17 April 2010,[23][24] followed by Stages 4 and 5 (from the Marymount to HarbourFront stations) on 8 October 2011.[25][26][27][28] A two-station extension to Marina Bay opened on 14 January 2012.[29][30][31][32]

On 17 January 2013, the Land Transport Authority (LTA) announced 'Circle Line Stage 6' which will 'close the circle', set to be completed by 2025.[33] The 4 km extension will run between Marina Bay and HarbourFront.[34][35] The extension will connect commuters between the HarbourFront to Marina Bay stations and expand the rail network to the southern edge of the Central Business District. On 29 October 2015, LTA announced the station locations for Stage 6, with the working names of the stations being Keppel, Cantonment and Prince Edward. Tenders were called for construction between 2016 and 2017.[36][37][38]

On 15 May 2017, the LTA invited the public to send in suggestions for names of the three MRT stations or propose to keep their current names.[39][40] The Keppel and Cantonment stations kept their names, while Prince Edward station has been changed to 'Prince Edward Road' station.[41]

Construction of Stage 6 commenced in late 2017. A joint venture – by China State Construction Engineering (The Singapore branch) and Nishimatsu Construction – won the contract to build the new Keppel MRT station and its associated tunnels.[42][43]

On 20 April 2004, a section of the tunnel being built for the Circle Line collapsed, when a retaining wall used in the tunnel's construction gave way. This incident occurred near the proposed site of the Nicoll Highway station, not far from the Merdeka Bridge. The accident left a collapse zone that was 150 metres (490 ft) wide, 100 metres (330 ft) long, and 30 metres (98 ft) deep. Four workers were killed, and three were injured.[44]

A criminal inquiry found the main contractor Nishimatsu Construction Company and joint venture partner firm Lum Chang Construction Company and their officers, as well as key Land Transport Authority officers responsible for the collapse. Several other officers and subcontractors were reprimanded and issued warnings in connection with the accident.[44]

As a result of this accident, the first phase of the Circle Line, previously scheduled to open in 2008, was completed in 2009 instead. The affected station has been shifted about 100 metres (330 ft) away from the accident site and is now located at Republic Avenue.

This accident also resulted in stricter safety regulations for the construction of all future MRT lines. The shifting of the Nicoll Highway station also meant it can no longer serve as a terminus for the Bukit Timah Line, partially influencing the creation of the current Downtown Line.

On 16 August 2007, the Building and Construction Authority (BCA) issued a stop-work order and revoked the contractor's tunnelling permit after a 7-metre (23 ft) stretch of two lanes close to the junction of Telok Blangah Road and Alexandra Road sank about 20 centimetres (7.9 in) that evening.[45]

A section of the road above a construction site near Holland Road caved in on the morning of 24 May 2008, creating a hole. The hole, directly in front of two private houses along Cornwall Gardens, measured 8 by 7 metres and was 3 metres deep. No one was injured, but the road was temporarily closed to traffic.[46]

On 20 September 2011, a power fault disrupted train services at all 16 stations on the Circle Line. The four-hour delay left thousands of commuters stranded during rush-hour. It was reported that leaks and a damaged electrical cable along the Circle Line were the cause of the disruption.[47] The disruption started at about 5.30 am. Train services were gradually restored from 8 am and all services were restored just before 10 am. Dakota and Mountbatten stations were the last two to resume operations.[48] Investigations were carried out, and the fault was traced back to a faulty cable beneath the platform level at Dakota station.[49] 27,000 passengers were affected by the disruption during the four hour delay, with bus bridging services plying the Circle Line route.[50]

In late August 2016, intermittent signal interference led to a five-day series of train disruptions. The issue reappeared in November.[51][52] A team of data scientists explored the data and discovered via a Marey Chart visualization that it was caused by hardware problems, sending errant signals from a "rogue" train, PV46.[53][54]

Geographically accurate map of the Circle line.

The 35.5-kilometre (22.1 mi) Circle line forms an incomplete loop from Dhoby Ghaut in the Central Region of Singapore, north to Serangoon and Bishan, and south to HarbourFront, with a branch from Promenade to Marina Bay station which will be extended to HarbourFront in the future. The fully-underground circular route also makes several links with the other MRT lines.[55] The line begins at Dhoby Ghaut station, which has an interchange with the North South and North East lines,[56] going eastwards and paralleling Bras Basah Road and Raffles Boulevard, before joining the Circle line extension at Promenade station, which also interchanges with the Downtown line.[57][58] From Promenade station, the line goes northwards and towards the east, passing beneath the Kallang Basin.[59] Between the Stadium and Dakota stations, the line parallels Stadium Boulevard and Old Airport Road, then the line continues northwards and follows the route of Paya Lebar Road and Upper Paya Lebar Road between the Paya Lebar (which interchanges with the East West line) and Tai Seng stations.[60]

The line curves and continues westwards between the Bartley and Marymount stations, also interchanging with the North East and North South lines at Serangoon and Bishan stations respectively,[61] and then it continues in a general southwest direction between Caldecott and Kent Ridge,[62]passing through Bukit Brown Cemetery between the Caldecott and Botanic Gardens stations.[63] The line also interchanges with the Downtown line at Botanic Gardens station and the East West line at Buona Vista station. After Kent Ridge station, the line curves eastwards, paralleling the West Coast Highway and then terminating at HarbourFront station, where it interchanges with the North East line.[64]

From 2026, upon the completion of Stage 6, the Circle line will continue westwards from Harbourfront, paralleling Keppel Road and Ayer Rajah Expressway, and joins the Circle line extension at Marina Bay station.[65] The Circle line extension from Marina Bay to Promenade station generally parallels the Downtown line and Bayfront Avenue, also passing underneath Marina Bay Sands at Bayfront station, which it serves and has cross-platform interchange with the Downtown line.[66]

Station Number	Station Name	Images	Interchange/Notes
CC1  NS24  NE6	Dhoby Ghaut		Interchange with the North South line and the North East line
CC2	Bras Basah
CC3	Esplanade
CC4  DT15	Promenade		Interchange with the Downtown line Change for train services towards Bayfront or Marina Bay stations
CC5	Nicoll Highway
CC6	Stadium		Marina Bay shuttle terminus during off-peak hours
CC7	Mountbatten
CC8	Dakota
CC9  EW8	Paya Lebar		Interchange with the East West line
CC10  DT26	MacPherson		Interchange with the Downtown line
CC11	Tai Seng
CC12	Bartley
CC13  NE12	Serangoon		Interchange with the North East line
CC14	Lorong Chuan
CC15  NS17	Bishan		Interchange with the North South line
CC16	Marymount
CC17  TE9	Caldecott		Interchange with the Thomson-East Coast line (2020)
CC18	Bukit Brown		Reserve station to be open at a later date
CC19  DT9	Botanic Gardens		Interchange with the Downtown line
CC20	Farrer Road
CC21	Holland Village
CC22  EW21	Buona Vista		Interchange with the East West line
CC23	one-north
CC24	Kent Ridge
CC25	Haw Par Villa
CC26	Pasir Panjang
CC27	Labrador Park
CC28	Telok Blangah
CC29  NE1	HarbourFront		Interchange with the North East line
Stage 6 (under construction, to be ready by 2025)
CC30	Keppel
CC31	Cantonment
CC32	Prince Edward Road
Circle Line extension
CE1  DT16   CC34  DT16  (from 2025)	Bayfront		Cross-Platform Interchange with the Downtown line
CE2  NS27  TE20   CC33  NS27  TE20  (from 2025)	Marina Bay		Interchange with the North South line and the Thomson-East Coast line (2021)

The Circle Line's numbering scheme reserves station code "CC18" for future use.