The temporary traffic reconfiguration along Ang Mo Kio Avenue 3 is required to facilitate additional recovery works, said the Land Transport Authority.
SINGAPORE: Traffic arrangements around AMK Hub will be reconfigured for about 18 months from Nov 14, after unexpected obstructions were found during tunnelling works for the Cross Island Line (CRL).
The changes along Ang Mo Kio Avenue 3 are expected to remain in place until May 2028, and the Land Transport Authority (LTA) said on Friday (Oct 16) that it would deploy measures to manage traffic and minimise inconvenience for motorists, commuters and residents.
According to LTA, the 18-month timeline is based on current assessments and may be adjusted as recovery works progress.
AMK Hub is connected to Ang Mo Kio MRT station and the bus interchange.
To ensure the safety of road users and provide enough working space for investigations and recovery works, traffic flows along Ang Mo Kio Avenue 3 will change.
The eastbound carriageway between the mall's pick-up and drop-off point and the junction with Ang Mo Kio Avenue 8 will become a bus-only lane.
In the opposite direction, the westbound carriageway will be reduced from three lanes to two.
Motorists who currently travel east along the affected stretch of Ang Mo Kio Avenue 3 will have to use alternative routes.
During the morning peak, motorists heading towards the Central Expressway (CTE) can travel via Ang Mo Kio Avenue 1 or Ang Mo Kio Avenue 5 instead.
Depending on the route, this is estimated to add about one to five minutes to their journeys.
Those heading into AMK Hub during peak periods should expect longer queues and about 10 to 15 minutes of additional travel time, LTA said.
Motorists will still be able to access AMK Hub's basement car park and pick-up and drop-off point, although the entry and exit arrangements for the pick-up and drop-off point will change.
Traffic wardens and road signs will be deployed to guide motorists, with notifications also sent through their on-board units.
“Motorists are advised to plan their journeys ahead and follow traffic signs and directions at the affected area,” said LTA.
For pedestrians and public transport commuters, access to bus stops along Ang Mo Kio Avenue 3 will not be affected and barrier-free accessibility will be maintained.
However, the footpath along the eastbound side of Ang Mo Kio Avenue 3 will be closed, with pedestrians diverted through AMK Hub. The existing pedestrian crossing will also be relocated.
Ground-level access to the pedestrian overhead bridge on the AMK Hub side will also be closed. During the mall's operating hours, pedestrians can instead reach the bridge through Level 2 of AMK Hub.
Temporary covered linkways will be provided along diverted routes where practicable, while wayfinding and directional maps will be placed at pedestrian crossings. Traffic marshals will be deployed to guide commuters.
Signs will also be put up to indicate that businesses in the affected area remain accessible.
LTA said it has engaged residents, pedestrians and businesses in the area on the upcoming changes, with updates also shared through a Telegram group chat.
The authority added that traffic conditions would be monitored after the changes take effect, with further adjustments if necessary.
“We are also deploying additional resources, and will expedite works where they can be done safely,” said LTA.
TUNNELLING WORKS SUSPENDED
The traffic reconfiguration is needed to facilitate recovery works, after "unexpected ground obstructions" were discovered during tunnelling works for the construction of Ang Mo Kio station on the CRL.
The problems first surfaced in May, when "foreign materials" were unexpectedly discharged from the tunnel boring machine.
When workers inspected the machine, they found wire ropes entangled around its cutterhead. The ropes were removed and damaged cutters replaced, allowing tunnelling to resume.
However, between May and July, a total of 100 cutterhead interventions were required to clear more obstructions from the tunnel boring machine. About 800kg of wire ropes were extracted and 22 damaged cutters were replaced during this period.
The repeated encounters indicated that the obstruction was more extensive than initially assessed, LTA said.
Further investigations identified the obstructions as ground anchors beneath Ang Mo Kio Avenue 3.
Ground anchors are steel structures drilled into the ground to provide temporary support for retaining walls or other structures.
If encountered during tunnelling, they can damage the tunnel boring machine’s cutter tools, disrupt tunnelling and pose significant safety risks to underground works and the roads above, said LTA.
LTA has suspended tunnelling while it investigates the full extent of the obstructions and their origins. It is also assessing the impact of the obstructions on the timeline of CRL construction works.
Preliminarily, LTA will need to carry out recovery measures, including ground improvement works to strengthen and stabilise the ground along the tunnel alignment, before tunnelling can safely resume.
The obstructions will be progressively removed from within the tunnel boring machine while tunnelling proceeds in a safe and controlled manner.
Responding to queries from CNA, an LTA spokesperson said site investigations and engineering assessments, including soil investigation boreholes, are carried out before major infrastructure projects begin.
However, as boreholes sample ground conditions only at specific locations and intervals, slender ground anchors are difficult to detect unless a borehole intersects them.
In addition, the underground anchors were not reflected in the available records or as-built drawings and were therefore not identified before tunnelling.
LTA said there is currently no indication of similar undocumented ground anchors elsewhere along the tunnel alignment of the CRL, and that the issue is specific to this location.
Investigations and engineering assessments are ongoing, while the cost implications are being assessed.
"It would be premature to speculate on responsibility or potential actions at this stage. LTA will continue to assess the findings as they emerge and determine the appropriate next steps based on the facts established," said the authority.
It added: “The safety of residents, pedestrians, motorists and workers remains our foremost priority.
“The recovery works and traffic reconfiguration are necessary to ensure that investigations and engineering assessments can be carried out safely and thoroughly before tunnelling activities continue.”
It added that the area remains safe for public use and that ground conditions around AMK Hub and the surrounding area will be closely monitored while investigations and recovery works continue.
LTA's Cross Island Line group director Ng Choon Yeang said the priority now is to fully understand the situation and address the obstructions safely before tunnelling resumes.
"We understand the temporary traffic changes will cause some inconvenience to residents, motorists and businesses in the area … We thank the public for their understanding and patience, and we will keep the public updated as recovery works progress," he added.
"CAN PLACE A REAL BURDEN"
Research Assistant Professor Samuel Chng from the Singapore University of Technology and Design said the traffic changes would put more pressure on the remaining road capacity around AMK Hub, with longer queues expected at some junctions, particularly during peak periods.
The diverted traffic would also place additional demand on alternative routes towards the CTE during the morning peak, he said.
While LTA's assessments indicate that the surrounding road network can accommodate the diverted traffic, this does not mean journeys will be unaffected, he added.
"Much will depend on how queues develop at individual junctions and how quickly traffic management measures are adjusted in response," he said.
"The estimated additional 10 to 15 minutes relates specifically to motorists entering AMK Hub during peak periods; it should not be taken as a uniform delay for all journeys through the area."
He called 18 months a "substantial period in the everyday life of a town centre", and said that the significance of this reconfiguration lies in how it changes residents' familiar routines.
"An additional journey time or a longer walk may be manageable occasionally, but when repeated over many months, it can place a real burden on people, particularly those with limited mobility or tight work and caregiving schedules," he said.
When asked what could be done to help older residents navigate the pedestrian diversions safely and conveniently, Asst Prof Chng said changes to familiar routes can pose both physical and psychological challenges.
"A familiar route allows someone to travel confidently and independently," he said, adding that even short detours can be demanding for those using walking aids or carrying groceries.
Engagement with affected residents before the changes take effect will be "very important", Asst Prof Chng said.
He suggested walking the diverted routes with older residents, wheelchair users and caregivers, as well as providing face-to-face explanations and printed maps alongside digital updates.