North South MRT line

A plaque at Toa Payoh station commemorating the opening of the first phase of the Singapore MRT

The Mass Rapid Transit (MRT) originated from a forecast in 1967 by the planners of the State and City Planning Project,[2] which stated the need for a rail-based urban transport system in Singapore by 1992.[3][4]^:66[5] Following a debate on whether a bus-only system would be more cost-effective, then-Minister for Communications Ong Teng Cheong came to the conclusion that an all-bus system would be inadequate, as it would have to compete for road space in the land-scarce country.[6][7]

After deciding on a rail-based system, the construction of what would become the North South Line was given priority as the line passes through areas having a higher demand for public transport, such as the densely populated housing estates of Toa Payoh and Ang Mo Kio and the Central Area.[8][9] Construction of the MRT line (and also the MRT system itself) started on 22 October 1983,[10] and the first section from Yio Chu Kang station to Toa Payoh station opened on 7 November 1987.[11][12] At the inauguration ceremony, Ong Teng Cheong, who backed and commissioned the planning of the MRT system, attended the ceremony as a special Guest of Honour. Dr Yeo Ning Hong, the Minister For Communications and Information, inaugurated the start of MRT operations and announced it to be the "beginning" of the MRT system.[13]

Nine more stations from Novena station to Outram Park station via Raffles Place opened on 12 December that year.[14] The line was extended northward to Yishun station on 20 December 1988 as part of phase 2B[15] and it began independent operations on 4 November 1989 as the North South line when the extension to Marina Bay station was opened.[16][17]

Exterior of Woodlands MRT station

After the Branch line (from the Jurong East to Choa Chu Kang stations) opened in 1990, the Woodlands MRT line was envisioned so as to close the gap between Yishun and Choa Chu Kang stations.[19][20][21] Numerous changes were made to the number of stations for the extension mainly to accommodate the 1991 Concept Plan by the Urban Redevelopment Authority,[22][23] which aimed to make Woodlands a regional centre for northern Singapore. During the initial planning of the line, Sembawang station was only intended as a provisional station, to be built at a later date due to the underdevelopment of Sembawang, and construction began on 19 November 1992.[24] Sembawang station[25] and Kranji station[26] were later included in the construction after the second round of planning (construction began at the same time on 19 November 1992) and Sungei Kadut station was then omitted. Sungei Kadut will be built later if the town's population justifies the necessity for the station.[27]

During the construction, a total of 19 new trains were purchased for almost S$259 million for the new MRT line, designed by German company Siemens Aktiengesellschaft, to complement the 66 first generation C151 trains. There was also a need to level the land covered in thick vegetation in Kadut, Woodlands and Sembawang for the MRT line.[28]

With the official opening of the Woodlands extension on 10 February 1996 by then Prime Minister Goh Chok Tong, the Branch line was incorporated into the North South line.[20] The extension was built at a cost of $1.2 billion.[29]

Canberra MRT station.

The NSL platforms of the Bishan station went through major alterations to keep up with passenger demand for the station when it interchanged with the Circle line. A new air-conditioned platform was constructed to serve the southbound trains (heading towards Marina South Pier station), and was officially opened by the then-Minister for Transport Raymond Lim on 27 July 2008. The original platform is now dedicated to northbound train services (heading towards Jurong East station), and has been also air-conditioned, but sealed off from the south-bound platform.[30]

Under the Land Transport Master Plan 2008, the Jurong East Modification Project entailed the construction of a new platform and the addition of a fourth track to Jurong East station to reduce waiting times and crowding at the station during peak hours.[31] The modification project was completed on 27 May 2011.[32] The track and platform was initially opened during morning peak hours only, but since December 2011, they also operate during the evening peak hours.[33]

In the 2008 Land Transport Master Plan, the 1-kilometre (0.6 mi) North South Line extension was announced as one of the upcoming projects rolled out by the Land Transport Authority to expand Singapore's rail network.[34] The single station extension from Marina Bay to Marina South Pier station was opened on 23 November 2014.[35][36] This extension serves the Marina South Pier, the Marina Bay Cruise Centre Singapore, and future developments in the Marina Bay Downtown area.[37]

On 17 January 2013, the Land Transport Authority (LTA) announced that a feasibility study was conducted to construct Canberra MRT station.[38][39] The feasibility study was completed in 2014 and LTA announced Canberra as a new station.[40] Construction of Canberra station commenced on 26 March 2016.[41] The station, which is an infill station with side platforms, was built along an operational section of the line between Sembawang and Yishun. The station cost S$90 million to build,[42] and is meant to serve upcoming developments at the vicinity. Canberra station opened on 2 November 2019.[43]

On 3 March 2003, a 23-year-old man lost control of his vehicle along Lentor Avenue, crashed through the fence, and landed on a stretch of track between Yio Chu Kang and Khatib stations. The incident forced a train carrying hundreds of commuters to come to a screeching halt, but not before flattening the front of the car. The accident disrupted train services for more than three hours and cost SMRT between S$100,000 and $150,000 in damages and lost revenue.[44]

On 15 December 2011, services between Bishan and Marina Bay stations were suspended due to damage sustained on the power rail between City Hall and Dhoby Ghaut. Trains along the stretch were stalled and caused a service disruption until 11:40 pm on that day.[45][46] Two days later, a similar problem caused a seven-hour disruption between Ang Mo Kio and Marina Bay.[47][48] According to SMRT, the disruption was caused by damage to the third rail and the trains' collector shoes. Seven trains were damaged in this incident.[49] These two service disruptions on the North South line were both related to damaged rail, and became one of the worst disruption since SMRT's inception in 1987.[50]

On 7 July 2015, the North South and East West lines were temporarily disrupted due to massive power trips detected along the line. A cause of the disruption was due to damaged insulators which caused a failure to properly supply power.[51][52][53]

On 7 October 2017, a 20-hour long disruption of services started due to flooding in the tunnels between Braddell station and Bishan station due to a faulty drainage system, resulting in disruption of train services between Ang Mo Kio and Marina South Pier stations in both directions for several hours. A trackside fire between Raffles Place and Marina Bay stations further exacerbated the disruption. Train services between Marina South Pier and Newton resumed at about 9:20 pm on the same day, followed by Newton and Ang Mo Kio at around 2 pm the following day.[54] Although no injuries or casualties were reported, SMRT fired a total of eight employees from the maintenance crew, and incurred a S$2 million fine, following the incident.[55]

Locator maps of Brickland and Sungei Kadut stations

On 14 October 2020, train services from Jurong East to Woodlands stations ceased to operate for more than three and a half hours, owing to a faulty power cable, which affected the East West and Circle lines too. The power fault began at 7 pm and by 7:30 pm, commuters were stuck in the trains. Free bus bridging services were activated at all affected stations, and bus operators increased the frequency of regular services serving these areas. Service resumed at all stations along the North-South and East-West Lines at 10:35 pm.[56]

In the Land Transport Master Plan 2040 (LTMP2040), two new stations are projected to be built along the existing North South Line. Brickland station will be built between Bukit Gombak and Choa Chu Kang stations, while Sungei Kadut station will be built between Yew Tee and Kranji stations and provide an additional interchange with the Downtown line. Both are expected to be completed by the mid-2030s.[57][58][59][60]

Train services on the North South MRT line operates from approximately 5:30 am to around midnight daily. In general, during peak hours, train frequency is 2 to 3 minutes while during non-peak hours the frequency is reduced to 5 minutes throughout the entire route.[61] Each day, the first train begins service at approximately 5:15 am (5:35 am on Sundays and public holidays) from Jurong East station to Marina South Pier station. From Marina South Pier station, the first train going to Jurong East station begins service at 6:10 am (approximately 6:40 am on Sundays and public holidays). In the evenings, selected trains from Jurong East station will terminate at the Ang Mo Kio and Toa Payoh stations.[62] Selected trains departing from Marina South Pier station will also terminate at Kranji station in the late evenings.[63]

Train services on the North South Line are also subjected to maintenance and renewal works, usually on selected Fridays & Saturdays. Shuttle bus services may be provided throughout the duration of the early closures and late openings for affected commuters.[64][65] Operations of the North South Line are affected by the COVID-19 pandemic, due to the drop of ridership.[66][67]

Geographically accurate map of the North South MRT line.

The North South line forms an incomplete loop from Jurong East in the West Region of Singapore, north to Woodlands and Sembawang, and south to the Central Area.[68] It is 45 kilometres (28 mi) long and is predominantly double-tracked, but certain short sections at the Woodlands, Yishun and Ang Mo Kio stations widen to three tracks,[69][70][71] and four tracks at Jurong East station.[72] The line begins above ground at Jurong East station[73][74] from where it continues north on a set of elevated viaducts, with the exception of a short tunnel between the Bukit Batok and Bukit Gombak stations,[75] and a surface section of track between the Bukit Gombak and Choa Chu Kang stations.[76] The line curves from the Yew Tee to Kranji stations and continues eastwards, paralleling Woodlands Avenue 3 (which the line briefly cuts underneath between Kranji and Marsiling stations)[77] and Avenue 7 main roads.[78]

After Sembawang station, the line follows the route of Canberra Link and Yishun Avenue 2, curving southwards. Between Khatib and Yio Chu Kang stations parallel to Lentor Avenue, the line continues at surface level; this section is the longest distance between any two MRT stations in Singapore.[79] The line continues above ground for the Yio Chu Kang and Ang Mo Kio stations, then it goes back to surface level for Bishan station, the MRT system's only at-grade station. A branch line to Bishan Depot exists between the Ang Mo Kio and Bishan stations.[80] After Bishan, the line goes underground through the Central Area. The North South line runs parallel to the East West line at the City Hall and Raffles Place stations, which are also cross-platform interchanges to the East West line. The line terminates at Marina South Pier.[81][74]

The line serves 27 stations across 45 kilometres (28 mi) of track, and station codes for the line are red, corresponding to the line's colour on the system map.[68][82] 11 stations, from Braddell to Marina South Pier stations, are underground, with the rest being at grade or above ground.[83] With the exception of Bishan, Braddell and Canberra stations, the other stations have island platforms.

Station Number	Station Name	Image	Interchange/Notes
NS1  EW24  JE5	Jurong East		This station was upgraded with new platform and new track on 27 May 2011.[84] Cross-Platform Interchange with the East West line Interchange station with the Jurong Region line (2027)
NS2	Bukit Batok
NS3	Bukit Gombak
NS3A	Brickland		Future infill station (mid 2030s)
NS4  BP1  JS1	Choa Chu Kang		Interchange station with the Bukit Panjang LRT and the Jurong Region line (2026)
NS5	Yew Tee
NS6  DT–	Sungei Kadut		Future infill station. Interchange station with the Downtown line (mid 2030s)
NS7	Kranji
NS8	Marsiling
NS9  TE2	Woodlands		Interchange station with the Thomson-East Coast line
NS10	Admiralty
NS11	Sembawang
NS12	Canberra		Infill station, reduces congestion on both Yishun and Sembawang MRT Stations
NS13	Yishun
NS14	Khatib
NS15	Yio Chu Kang
NS16  CR11	Ang Mo Kio		Interchange station with the Cross Island line (2029)
NS17  CC15	Bishan		This station was upgraded since 2007 and was split into two side platforms between 27 July 2008 and 23 May 2009. Interchange station with the Circle line
NS18	Braddell
NS19	Toa Payoh
NS20	Novena
NS21 – DT11	Newton		Connected to the Downtown line
NS22  TE14	Orchard		Interchange station with the Thomson-East Coast line (2021)
NS23	Somerset
NS24  NE6  CC1	Dhoby Ghaut		Interchange station with the North East and Circle lines.
NS25  EW13	City Hall		Cross-Platform Interchange with the East West line
NS26  EW14	Raffles Place		Cross-Platform Interchange with the East West line
NS27  CE2  TE20	Marina Bay		Interchange station with the Circle line and the Thomson-East Coast line (2021)
NS28	Marina South Pier

A variety of rolling stocks on the NSL

Various older generation rolling stock of the NSL parked at Bishan Depot.

The newer rolling stocks of C151B and C151C at Choa Chu Kang station.

Trains on the NSL operate with a six-car formation, with an electrification of 750 V DC powered by a third rail. With the exception of the C651, the current rolling stock was manufactured by Kawasaki Heavy Industries, in a joint venture with CRRC Qingdao Sifang for the subsequent rolling stocks of the C151A, C151B and C151C.[85] When the initial line opened, the rolling stock of the North South Line consisted of C151 trains only. The C651 was introduced during the Woodlands extension to complement the existing 66 C151 trains.[86] The third-generation C751B trains were delivered in 2000.[87][88] In 2011, the fourth-generation C151A was introduced, increasing the passenger capacity of both the North South and East West lines by 15%.[89][90][91] The C151A contract was the first successful joint venture between Kawasaki Heavy Industries and CSR Qingdao Sifang in the international market.[92]

As part of efforts to further increase passenger capacity on the line, newer C151B and C151C rolling stock was subsequently delivered in 2017[93] and 2018[94] respectively. The introduction of the C151B saw the introduction of STARiS 2.0, which is also seen in subsequent rolling stocks.[95] The C151C is also the first MRT rolling stock on the NSEWL to be fitted with fold-up seats, in addition to the current features of the C151B.[96][97]

Another generation of rolling stock, the Bombardier Movia CR151, will be delivered from 2021 to 2026, to replace the C151, C651 and C751B trains which will be retired. The CR151 will be the first rolling stock on the North South line to be manufactured by Bombardier, which has also supplied trains for the Downtown MRT line.[98][99] The current rolling stock of the NSL is housed in Bishan Depot, which provides train maintenance, inspection and overhaul facilities,[100] and in Ulu Pandan Depot.[101][102]

Initially, the North South line used a semi-automatic signalling system consisting of the Westinghouse fixed block signalling system with automatic train control under automatic train operation GoA 2.[103][104][105] However, the ageing system had undermined the rail reliability on the line, requiring the NSL to upgrade its signalling system.[106] Since 2019, the North South line is fully equipped with Thales SelTrac Communications-based train control moving block signalling system[107] with automatic train control under automatic train operation (ATO) GoA 3 (DTO).[108] The subsystems consist of automatic train protection to govern train speed, NetTrac MT Automatic Train Supervision (ATS) to track and schedule trains and a Computer-based interlocking system that prevents incorrect signal and track points to be set.[109]

A new moving-block signalling system, supplied by Thales, replaced the ageing fixed-block signalling system on the North South line. The upgrading works were completed in phases from 2016. With the upgraded signalling system, trains are now able to run closer to each other.[110][111] The new system was tested on the evening of 28 March 2017. Train services were paused for ten minutes as the old signalling system was being changed to the new system.[112] From 16 April 2017, the new system commenced full-day testing on Sundays for two months. The new C151B rolling stock were first introduced to the line on these testing days.[113] Since 28 May 2017, the new signalling system has been operating full-day on the North South line.[114] The old signalling system then ceased operations on 2 January 2019.[102]

Full-height platform screen doors at Toa Payoh station.

When the line was first opened, full-height platform screen doors supplied by Westinghouse were installed at underground stations. These doors serve to prevent suicides, enable climate control within the station, better security control by restricting access to the tunnels and tracks and for overall passenger safety considerations.[115] The authorities initially rejected calls for platform screen doors to be installed at elevated stations by casting doubts over functionality and concerns about the high installation costs.[116] Nevertheless, the LTA reversed its decision and made plans to install half-height platform screen doors on elevated stations on 25 January 2008.[117][118] The first platform screen doors by ST Electronics were installed at Pasir Ris, Jurong East and Yishun stations in 2009 as trial runs.[119] Subsequently, installation began in May 2011 at Ang Mo Kio station. On 14 March 2012, platform screen doors became operational at all elevated stations on the North South line.[120]

The NSL was built with wooden sleepers, which needed to be replaced when they neared the end of their lifespan of 15 to 25 years. The replacement sleepers, made out of concrete, have a significantly longer lifespan and enable smoother and safer rides.[121] Since 2014, train services on the line have ended earlier for critical maintenance works, with the exception of a break between September 2016 and December 2017.[122]

Trains on the NSL are powered via a third rail. However, constant contact between the train's Current Collector Devices (CCD) and the line saw the need for replacement works on the third rail, which were completed in August 2017.[121][123] The new third rail replaced its 30-year-old predecessor, which was used since the opening of the line. The new electrical system is expected to make train services more reliable.[124]