SINGAPORE - A busy traffic junction near Marymount Community Club will be turned into a signalised roundabout for about a year, from April 30 until the second quarter of 2024.

This will allow construction of the upcoming North-South Corridor (NSC), which will include underground road tunnels located beneath the junction, to be carried out at a faster pace, the authorities said.

In a notice to residents dated March 30, the Land Transport Authority (LTA) said the signalised roundabout, akin to that at Newton Circus, will be constructed at the existing cross junction of Marymount Road, Sin Ming Avenue and Bishan Street 22.

The cross junction will be reinstated once the temporary roundabout has served its purpose.

Road works for the roundabout will be carried out in the day and at night until April 30. These include the installation of traffic lights and the diversion of existing footpaths and pedestrian crossings in the area.

“We seek your kind understanding that intermittent noise and dust may arise during the works,” LTA said in its notice, adding that there will also be lane closures during this time.

Temporary barricades and directional signs will be set up to warn motorists of the traffic changes and guide pedestrians in using the new footpaths and pedestrian crossings, LTA said.

It added: “We will work with our contractor on the necessary mitigation measures to minimise the inconveniences.”

In response to queries, LTA said regular users of the affected junction are being given ample notice, with notifications put up a month ahead of time at all four approaches towards the intersection, as well as at roads farther away such as Ang Mo Kio Avenue 1 and Ang Mo Kio Avenue 6.

Auxiliary police officers will be deployed to guide motorists through the new roundabout during the transition period, LTA added.

Asked why it decided to convert the cross junction, LTA said a roundabout is the most optimal traffic scheme as it minimises disruption and disamenities while creating sufficient space for tunnel works underground.

The alternative would be to have several stages of traffic diversion around the junction, which would extend the duration of the construction work and prolong the impact on motorists and pedestrians, an LTA spokesman said.

She added: “We will monitor the traffic flow after the reconfiguration closely and, if necessary, make further adjustments to traffic light timings and phasing to improve traffic flow.”

While roundabouts were once common in Singapore, there are only a handful of them remaining, and even fewer with traffic lights to control the flow of vehicles.

Besides Newton Circus, other signalised roundabouts here include the one below Tuas Flyover.

LTA has converted traffic junctions into roundabouts before to facilitate construction. In 1996, the junction of Holland Road, Farrer Road and Queensway was turned into a signalised roundabout for a year to allow the building of an underpass there.

It is also not the first time that a major traffic junction has been reconfigured to make room for NSC works.

In 2020, changes were made to the junction between Thomson, Newton and Moulmein roads in Novena, drawing complaints from motorists and commuters about the resulting inconveniences and traffic snarls.

These junctions were reconfigured again in 2022 to accommodate the next phase of NSC construction works.

Mr Calvin Ong, 20, passes the Marymount Road junction five to six times a week during his commute by bus or car. The part-time cinema cashier said the roundabout would likely increase travelling time, especially at the start when users are unfamiliar with the changes.

“It may be more inconvenient to walk around the place if there are a lot of changes, like closed paths or different paths,” he added.

Business owner Eugene Tan, 49, drives through the junction on weekends when running errands. He takes the MRT to work.

“I’m guessing the daily commute will be smoother at that junction if (it is) used safely and responsibly,” the Bishan resident said.

The key is for motorists to give way to others and slow down before entering the roundabout, he said, suggesting that speed bumps or other safety features be installed.

When completed from 2027 onwards, the 21.5km NSC promises to cut travel time from Woodlands, Sembawang, Yishun and Ang Mo Kio to the city by up to 30 minutes, and alleviate traffic along the Central Expressway.

Starting in Admiralty Road West and ending in East Coast Parkway near Republic Boulevard, the project mainly comprises an 8.8km expressway viaduct in the north and 12.3km of underground road tunnels in the south.

The surface roads along the NSC will be repurposed to feature dedicated bus lanes, a cycling trunk route and pedestrian paths, LTA said. This will create safer, more pleasant streets in neighbourhoods and support greener modes of transport, it added.

• Additional reporting by Rochelle Lee