North South MRT Line

The North South Line (NSL) is the first Mass Rapid Transit (MRT) line in Singapore. The line is 45 km long with 26 stations, including the upcoming North South Line Extension, slated to be completed by 2014. Traveling from one end of this line to the other end takes about one hour, and this line is coloured  red  on the rail map.

As the name implies, the line connects central Singapore to both northern and southern parts of the island. Cross-platform interchange with the East West Line is provided at Jurong East, City Hall and Raffles Place while transfer to the North East Line is possible via a linkway at Dhoby Ghaut. Connections to the Circle Line are provided at Bishan, Dhoby Ghaut and Marina Bay and a linkway via Esplanade. The North South Line will interchange with a future extension of the Downtown Line at Newton and with the future Thomson Line at Woodlands, Orchard and Marina Bay.

Initial system

 * 7 November 1987: Yio Chu Kang – Toa Payoh (First section opened)
 * 12 December 1987: Toa Payoh – Raffles Place
 * 20 December 1988: Yio Chu Kang – Yishun
 * 4 November 1989: Raffles Place – Marina Bay (start of separate North South Line & East West Line)
 * 10 March 1990: Jurong East – Choa Chu Kang (initially operated as the Branch Line of the East West Line)

Second phase of development (Woodlands Extension)
When the government did the initial planning of the Woodlands extension MRT line, Sembawang MRT station was only intended as a provisional station to be built at a later date due to the underdevelopment of the town and Kranji MRT station was not planned. But on the second round of planning, the government decided to build these station and omit Sungei Kadut station from the plan. Sungei Kadut station will be built later if the town's population justifies the necessity for the station.
 * 10 February 1996: Yishun – Choa Chu Kang (the Choa Chu Kang branch of the East West Line became part of the present North South Line)

Jurong East Modification Project (JEMP)
The Jurong East Modification Project consisted of the construction of a new platform and the addition of a fourth track to Jurong East Station. It has been in use since 27 May 2011. The North South Line currently utilises the new track and platform during the weekday morning peak hours from 7am to 9am only. From 27 December 2011, the platform and track will be utilised during the weekday evening peak hours. The new track and platform allows trains to be run at a higher frequency during weekday peak hours. Waiting time is now reduced from 4.5 minutes to 2.5 minutes. Along with the new platform and tracks, 22 Kawasaki Heavy Industries C151A trains will be added to the fleet to reduce waiting time and increase train frequencies. All 22 trains are in service as of February 2012.

North South Line Extension (NSLe)
A 1 km one station extension from Marina Bay which to be completed by 2014. The new Marina South Pier will be located near the Marina Bay Cruise Centre Singapore in Marina Bay. The then Minister for Transport, Raymond Lim, announced on 12 February 2009 that the completion date for the extension, initially due for completion in 2015, will be brought forward by a year to 2014. On 7 March 2012, Minister for Transport, Mr Lui Tuck Yew, gave his speech on Committee of Supply Debate 2012 in Parliament of Singapore that North South Line Extension expected to be completed in 2014.
 * 2014: Marina Bay – Marina South Pier

Possible future stations

 * A station between Yew Tee & Kranji - Sungei Kadut MRT Station, but however this was cancelled.
 * A station between Sembawang & Yishun

Half-height platform screen door installations
There were calls for platform screen doors to be installed at above-ground stations after several incidents in which passengers were killed 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 when the government announced plans to install half-height platform screen doors on the above-ground stations in January 2008, citing lower costs due to it becoming a more common feature worldwide. They were first installed at Jurong East, Pasir Ris and Yishun stations in 2009 as trial runs.

By 14 March 2012, all above-ground stations have been retrofitted with the doors and are operational.

Line disruptions
On 15 December 2011, services between Bishan and Marina Bay stations were suspended due to 40 metres of the power rail being damaged between City Hall and Dhoby Ghaut stations. Trains along the stretch were stalled, causing a disruption to the train service for almost 5 hours. Train service fully resume at 11.40pm.

On 17 December 2011, a similar fault caused a 7-hour disruption between Ang Mo Kio and Marina Bay stations. 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.

These two service disruptions on the North-South Line were the worst ever since SMRT started operation for 24 years.

Rolling stock
Trains operating on the line, i.e., the C151s, the C651s, C751Bs and C151As. These trains operates from the Bishan Depot which serves maintenance and train overhaul facilities for trains along the North South Line.

Additional information

 * During peak hours, there are additional northbound services from Marina Bay to Yishun.
 * Additional special event services will operate between Marina Bay and either Yishun or Ang Mo Kio.
 * Lunchtime Xpress services operate between Ang Mo Kio and Marina Bay on weekdays (excluding public holidays) between noon and 2 pm.
 * The last two trips after Jurong East will go to Ang Mo Kio before the official last train to Kranji.