North–South Corridor, Singapore

The North–South Corridor (NSC), originally conceptualised as the North-South Expressway (NSE), is an under-construction expressway that will be the 11th of Singapore's network of expressways when completed. The North South Corridor will serve increasing traffic along the north-south corridor that is currently served by the Central Expressway (CTE). The 21.5 km expressway is expected to cost about S$7.47 billion when fully completed in 2029 as North-South Corridor and will connect the East Coast Parkway (ECP) with the northern parts of Singapore.

The NSC will have a total of 16 entrances and 17 exits to connect towns along the north-south corridor—Woodlands, Sembawang, Yishun, Ang Mo Kio, Bishan and Toa Payoh—with the city centre. The NSC will also provide links to existing expressways, including the Seletar Expressway (SLE), Pan-Island Expressway (PIE) and East Coast Parkway (ECP).

The NSC will be Singapore's first expressway conceived as an "integrated transport corridor", featuring dedicated bus lanes and cycling trunk routes integrated with a traditional expressway. The NSC Expressway (previously conceived as the NSE) consists of an 8.8 km viaduct in the north running from Admiralty Road West to Lentor Avenue, a 0.4 km at-grade section at Lentor Avenue, and a 12.3 km underground tunnel portion that runs until East Coast Parkway. Additionally, the surface streets that run along the underground tunnel of the NSC will see road lanes reprioritised for walking, cycling, public transport and community spaces.

According to the Land Transport Authority (LTA), the continuous bus lanes along the NSC will be able to reduce bus travelling times from Woodlands, Sembawang, Yishun and Ang Mo Kio to the city by up to 30 minutes through morning and evening peak express bus services, and also make bus connections between residential towns along the NSC faster by allowing intra-town buses to leverage the ramps and bus lanes on the surface. A cycling path along the entire stretch of the highway will link up the Park Connector Networks and dedicated cycling path networks within HDB towns along the entire corridor to the city centre.

When first conceptualised in 2011, the NSE was initially targeted to be ready by 2020. In January 2016, the NSE was then reconfigured to instead be part of the NSC, with a new completion date of 2026 set for the NSC. However, due to significant delays in construction, the deadline has been pushed back multiple times. It is now expected for the viaduct (at the northern terminus of the expressway) to be opened in 2027, and the underground tunnels (at the southern terminus of the expressway) to be opened in 2029.

Plans
On 30 January 2008, the expressway was first announced by then Minister for Transport Raymond Lim as the North-South Expressway (NSE), as part of a major review of Singapore's transport network by the Land Transport Authority (LTA). It was then expected that the NSE would be completed by 2020, and would reduce travel time to the city for residents in the north by up to 30%

On 19 January 2011, the government gave the go-ahead for the alignment of the northern section consisting of viaducts, surface and tunnel from Admiralty Road West to Toa Payoh Rise, which is expected to complete in 2020, construction is expected to start in 2013 with the easiest acquisition. On 15 November 2011, the government gave the go-ahead for the alignment of southern section consisting of the full tunnel to ECP, and the construction was further delayed, to "after the demolition of Rochor Centre" in 2017 and construction is expected to begin in 2018 for completion in 2025, then subsequently delayed to 2026 during the groundbreaking ceremony of North-South Corridor and further delayed to 2028 due to COVID-19 pandemic. Then Minister for Transport Khaw Boon Wan outlined the ministry's plans to reconfigure the NSE as part of the North-South Corridor (NSC), an integrated transport corridor with one lane out of the three-lane highway to be dedicated for express bus services, as well as to have cycling and pedestrian paths that run along the NSC.

Land acquisitions and demolitions
The North-South Corridor entails the acquisition of Marymount Terrace terraced houses and Rochor Centre in the initial phase. Terraced houses were the easiest to move, HDB flats requires the construction of the replacement which is due to the construction delays for North-South Corridor. A total of 567 flats and 187 rental shops and eating houses were vacated by 31 December 2016. The four blocks of HDB flats eventually began demolition on 26 June 2018, and was targeted to finish by April 2019.

In August 2016, several units in the Ellison Building which was built in 1924, was considered for partial demolition and reconstruction after the completion of the NSC, despite its previous conservation gazette in 2008 by the URA. This sparked concerns from several heritage groups in Singapore including the Singapore Heritage Society and International Council on Monuments and Sites (Singapore), slamming the decision to reconstruct as it would be equivalent to the "falsification of historical artefacts", while also bringing the efficacy of conservation gazettes into question. The URA then came up with a revised plan in February 2018 to instead demolish and reconstruct part of the façade of only one unit, compared to the original plan of demolishing and reconstructing three full units in the building.

In April 2021, another four-storey building along Thomson Road, comprising 12 residential units and 4 shops, was acquired to make way for construction of the NSC. Unit owners were initially instructed to vacate the premises temporarily for a period of two years until excavation works were completed for safety reasons, but it was found that the building's concrete strength was lower than safely required in order to withstand excavation works for the tunnel beneath the building, and thus was instead chosen to be acquired and demolished. This sparked some unhappiness with the unit owners who were looking forward to a collective sale on the open market, since the proceeds were expected to be higher than the compensation that they would have received from the land acquisition.

Construction
The first contract for the NSC was awarded in November 2017, which expected the construction for the section of the tunnel between Toa Payoh Rise and Novena Rise to commence in 2018. Several other contracts were also awarded for the construction of various sections of the underground tunnel throughout the whole of 2018 to January 2019.

The contracts for the viaduct portion of the NSC were awarded later, with three contracts awarded in December 2019, with works expecting to begin in early 2020.

On 1 July 2023, it was announced that the NSC will be completed in two phases instead, starting with the viaduct segment which would be completed by the previous expected completion date of 2027, followed by the underground tunnel segment which would be delayed by another two years and completed by 2029 instead. Reasons cited for the delay include the COVID-19 pandemic along with challenging soil conditions.

On 17 September 2023, an accident occurred resulting in the death of a 41-year-old construction worker at the worksite of Cavenagh Road when a pallet of gas cylinders toppled.

Impact during construction
In order to support the construction of the North-South Corridor, several roads were temporarily rerouted or diverted during the process:


 * With the demolition of the underpasses around the Novena area, it was announced that the major traffic junction at Novena linking Newton Road, Moulmein Road and Thomson Road, will be adjusted to make way for the construction of expressway tunnels.


 * On 30 March 2023, it was announced that a traffic junction between Marymount Road, Sin Ming Avenue and Bishan Street 22 would be converted into a signalised roundabout temporarily to speed up construction on the underground road tunnel beneath the junction from 30 April 2023 until Q2 2024.

During the construction, noise complaints were received by the LTA that construction works did not adhere to requirements to cease after 10pm and during weekends. In response, the LTA mentioned that there may be exceptions to the stoppage requirement in the case of "safety critical works". In addition, more noise barriers were deployed in the Novena area following the complaint.
 * On 4 October 2023, it was announced that Marymount Flyover will be temporarily closed for construction works for the North-South Corridor starting 8 October 2023 until 2029.

Route
Based on the plans released by LTA as of the NSE alignment released on November 2011, the route that the 21.5 km NSC expressway will take is as follows:


 * Viaduct: 8.8 km running from Admiralty Road West to Lentor Avenue/SLE
 * The northern terminus of the NSC commences at Admiralty Road West, and runs southwards along Woodlands Avenue 8/Gambas Avenue/Sembawang Road, before joining Lentor Avenue.
 * The portion of the viaduct that runs along Lentor Avenue is also expected to run parallel to the North–South MRT line.
 * At-grade: 0.4 km intersecting at Lentor Avenue/SLE
 * Three off-ramps are planned, with two off-ramps going north/south-wards along Lentor Avenue, and one off-ramp going westwards towards SLE/BKE.
 * One on-ramp is planned from the SLE traveling westwards to join NSC towards the north.
 * Tunnel: 12.3 km running from Lentor Avenue/SLE to ECP, Republic Avenue, Nicoll Highway
 * The underground tunnel starts at Lentor Avenue/SLE and runs southwards along Ang Mo Kio Avenue 6/Marymount Road, passing Toa Payoh Rise, before joining Thomson Road and Bukit Timah Road running parallel to the Central Expressway, continuing along Ophir Road, before joining ECP, Republic Avenue, and Nicoll Highway at its southern terminus of the NSC.
 * On Marymount Road, the tunnel will be integrated with the MRT station box for the Teck Ghee station on the upcoming Cross Island MRT line.
 * One on-ramp is planned from the PIE traveling eastwards to join NSC towards the south, as well as one off-ramp going northwards to join the PIE traveling westwards.

Planned entrances and exits
{|class="wikitable" ! Location || Destinations || Notes Lentor Avenue (southbound) and BKE Lentor Avenue (northbound) Bukit Timah Road and (northbound)
 * rowspan=3|Sembawang || Admiralty Road West || Northern terminus
 * Woodlands Avenue 8 || Northbound exit only
 * style="background-color: #ffdddd"|Gambas Avenue and Woodlands Avenue 12
 * style="background-color: #ffdddd"|Northbound exit and southbound entrance only
 * rowspan=2|Yishun
 * style="background-color: #ffdddd"|Sembawang Road
 * style="background-color: #ffdddd"|Northbound exit and southbound entrance only
 * style="background-color: #ffdddd"|Sembawang Road, Yishun Avenue 1 and Mandai Avenue
 * style="background-color: #ffdddd"|Southbound entrance only
 * rowspan=2|Ang Mo Kio
 * style="background-color: #ffdddd"|
 * style="background-color: #ffdddd"|Sembawang Road, Yishun Avenue 1 and Mandai Avenue
 * style="background-color: #ffdddd"|Southbound entrance only
 * rowspan=2|Ang Mo Kio
 * style="background-color: #ffdddd"|
 * rowspan=2|Ang Mo Kio
 * style="background-color: #ffdddd"|
 * style="background-color: #ffdddd"|Southbound and northbound exits Northbound entrance from only
 * style="background-color: #ffdddd"| Ang Mo Kio Avenue 6
 * style="background-color: #ffdddd"|Northbound entrance only
 * Bishan || Marymount Road ||
 * Toa Payoh
 * style="background-color: #ffdddd"|Thomson Road
 * style="background-color: #ffdddd"|Northbound exit and southbound entrance only
 * Novena
 * style="background-color: #ffdddd"| (Tuas)
 * style="background-color: #ffdddd"|Northbound exit and southbound entrance only
 * Kallang || Kampong Java Road, Bukit Timah Road and (southbound)
 * Novena
 * style="background-color: #ffdddd"| (Tuas)
 * style="background-color: #ffdddd"|Northbound exit and southbound entrance only
 * Kallang || Kampong Java Road, Bukit Timah Road and (southbound)
 * Kallang || Kampong Java Road, Bukit Timah Road and (southbound)
 * rowspan=3|Downtown Core
 * style="background-color: #ffdddd"|Ophir Road
 * style="background-color: #ffdddd"|Southbound exit and northbound entrance only, latter from Rochor Road
 * style="background-color: #ffdddd"|Nicoll Highway
 * style="background-color: #ffdddd"|Northbound entrance only
 * Republic Avenue and Republic Boulevard || Southern terminus
 * style="background-color: #ffdddd"|Northbound entrance only
 * Republic Avenue and Republic Boulevard || Southern terminus
 * Republic Avenue and Republic Boulevard || Southern terminus