3 hours a night: What it took to close the Circle Line loop while running it

Ng Chan Cheok wakes at four every morning to check his phone. Most days, he is greeted by what he wants to see: no notifications.

That means overnight works on the Circle Line went well.

“I dread my phone ringing,” Ng says with a laugh. “A text message is still okay, but the moment it rings, it usually means big trouble.”

The 57-year-old is SMRT’s head of Circle Line (CCL). Maintenance of trains and tracks can only be done every day between 1.30am and 4.30am, known as the engineering hours between the last and first train service.

“Many critical interactions – like if a train cannot start or a system isn’t working – happen around this time,” he explains.

Early mornings have been part of Ng’s routine since he took on the role in 2022. All active train lines require regular maintenance work during engineering hours.

But there is an additional layer of complexity for the CCL: Integrating three new MRT stations and 23 new trains into its network in those same three hours.

These stations – Keppel, Cantonment and Prince Edward Road – will open on July 12, connecting Harbourfront and Marina Bay stations and completing the CCL.

Commuters, especially those staying in the west, can expect shorter journeys to the city centre, says the Land Transport Authority (LTA).

LTA builds and owns assets such as the CCL MRT stations and trains, while SMRT operates and maintains them.

A balancing act

The CCL began operations in 2009, progressively opening in stages. In 2025, there were over 500,000 rides on the line on an average weekday, according to LTA.

The line cannot stop running; maintenance must continue even as engineers install and test new systems for the final stretch of the line, known as CCL6, explains Ng.

This makes the project different from a new MRT line, he says, where engineering work can happen anytime without affecting maintenance or service.

On the CCL, every task must be done in the same overnight window. These include:

“That is the main tension we face,” says Ng. He chairs a weekly meeting to deconflict track access between teams. Corrective maintenance always comes first, then time-sensitive project work.

Regardless of what overnight work was done, the systems must be handed back in “green”, or full working order, prior to passenger service, says Isaac Goh, 34, SMRT’s deputy engineering maintenance manager of the CCL.

From the operations control centre, Goh oversees an integrated system which monitors critical features that keep the line running, including power supply, communications and station facilities.

His team manages the transition back to live operations after any overnight work, making sure the system is stable before the first train of the day rolls out.

Lapses in the process can affect the monitoring of train movements from SMRT’s operations control centre, he says, and essential systems like station lighting and public announcements.

What the completed loop means for you

The Circle Line (CCL) will become a complete loop on July 12 with the opening of three stations: Keppel, Cantonment and Prince Edward Road.

Planned in the 1990s, the CCL was designed to intersect with all existing lines at interchange stations, says Priscilla Chan, group director of policy and planning at the Land Transport Authority.

This enhances the connectivity of the network, says Chan, giving commuters more travel options between outer urban areas without having to pass through the city centre.

CCL6, the final stage of the line, was planned to serve future developments along the Keppel Road corridor, she adds.

This includes the Greater Southern Waterfront, which will be developed as an extension of the Central Business District after port operations at Tanjong Pagar, Keppel, Brani and Pasir Panjang relocate to Tuas.

Originally slated for completion by 2025, the CCL6 project was delayed by the Covid-19 pandemic.

The completed loop will shorten travel times between the west and the city centre, as well as areas in the east.

“For example, a commuter travelling from Telok Blangah to Marina Bay currently has to transfer between the CCL, North East Line (NEL) and Thomson-East Coast Line (TEL),” says Chan. “With the completion of CCL6, the same journey can be made on a single train ride, saving around 10 minutes.”

One commuter looking forward to the change is composer-pianist Jonathan Shin, 34.

For over a year, Shin has been travelling from his home near Tanjong Katong station to Yong Siew Toh Conservatory at NUS, where he teaches and uses its facilities almost daily.

His current commute involves transfers from the TEL to the NEL at Outram Park, and from NEL to CCL for the final leg to Kent Ridge station, where NUS is. It takes about an hour each way.

With the loop completed, Shin can stay on the TEL to Marina Bay before making a single transfer to the Circle Line. He thinks the new route could save him up to 15 minutes each way.

“I depend on the train a lot,” says Shin. “Now that it’s just one transfer, my journey won’t be interrupted as much, so I’ll have more time to sit on the train and work on my music.”

A race against time

The handover is not instant. Switching between daily operation and integration testing software can take over an hour, Ng explains, eating into the three-hour window.

During key project milestones, more time was needed for integration testing. Early closures and late openings on the CCL were implemented on some Fridays and weekends from September to December 2025, and from April to May 2026.

Even with that buffer, the margin for error stays small. The CCL uses three-car trains, unlike the six-car trains used on the North-South, East-West and North East Lines, explains Ng.

A brief delay can lead to crowds building up quickly at interchange stations like Bishan and Serangoon, where commuters transfer from other lines to CCL, he adds.

Beyond CCL6, the SMRT team was also coordinating with LTA on tunnel strengthening works at Dakota, Mountbatten and Paya Lebar stations from January to April.

Ng recalls a close shave in April during the works. An engineering train had accidentally shifted onto the wrong segment of the track, triggering a safety system that blocked all nearby trains from moving to avoid a collision.

This would have affected passenger trains due to depart for morning service.

“Fortunately, we mobilised people and managed to safely move the maintenance train before our start time, avoiding a major service disruption,” he says.

Despite the challenges, both Ng and Goh are excited to see the project come to fruition, bringing convenience to more Singaporeans.

Goh used to analyse backend data at SMRT before taking on his current role in 2025. While frontline work can be more stressful, he says it is rewarding to help provide commuters with shorter journeys. “It’s a different kind of pressure, but seeing this through makes it worth it,” he says.

Ng is proud of what the team has achieved: “Over the last two years, we’ve improved our processes and systems significantly.”

The reliability of the CCL improved the most across the entire MRT network in May, according to LTA’s rail reliability report published in June.

“We want to open the completed CCL on a high note,” he adds. But the work is not over.

“The (older parts of the) line is already 17 years old,” says Ng. “Over the next three to five years, a lot of the older signalling components and rolling stock will be progressively upgraded and replaced to enhance network reliability.”

This article was produced in partnership with SMRT.