Behind each MRT ride: How trains are overhauled, tracks maintained on North-South, East-West lines

SINGAPORE – Every four to five years, each of the 198 trains that operate on the North-South and East-West lines (NSEWL) is taken out of service for extensive maintenance that can take up to 21 days.

Typically, trains are overhauled for every 500,000km and 1,000,000km travelled, with different parts of the train restored at each mileage milestone.

At the 500,000km mark, parts such as the brakes and bogies – the undercarriage of a train – undergo servicing.

And at 1,000,000km, systems such as the door mechanism and couplers, which connect one carriage to the next, are thoroughly checked.

These are among as many as 13 major systems installed aboard a train.

SMRT said the maintenance intervals are determined by the respective manufacturers of the equipment. The operator’s maintenance planners track the utilisation of every train and schedule it for overhaul, it added. 

Every night, there are some 1,000 workers doing maintenance works on tracks, rail vehicles, facilities and signalling systems across 150 worksites, said SMRT.

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This includes works related to system upgrades, as well as testing and commissioning, it added.

The media got a close-up look at the train overhaul process on March 11 during a tour of Bishan Depot, which services the North-South Line operated by SMRT. The depot, where 700 engineers are based, is about the size of 55 football fields.

Rail maintenance has been in the spotlight after a series of train disruptions, including a major six-day breakdown on the East-West Line (EWL), also operated by SMRT, in September 2024.

In that incident, a defective axle box, a component on the undercarriage of a train, fell out near Dover station, causing one bogie to derail. It caused extensive damage to the tracks and equipment on the tracks, crippling a stretch of the EWL for six days.

On March 11, The Straits Times observed a train being pushed into Bishan Depot by a locomotive. For safety reasons, there is no power supply on the tracks leading into the workshop.

The train was guided by a crew into the workshop and lifted with special equipment so that the overhaul could begin.

Components that are removed are sent to SMRT’s Component Service Centres (CSC), each of which may specialise in different parts.

For example, the CSC at Bishan Depot is best equipped to deal with air-conditioning systems and couplers, while the depots at Kim Chuan and Tuas usually handle pneumatic systems and electric systems, respectively.

Pneumatic systems use compressed air or gas to power and control the movement of mechanical parts of a train, such as the brakes.

Overhauling the couplers at regular intervals is important, SMRT said. In the event of a collision, the train’s couplers can absorb the shock.

Among other things, the couplers are checked for cracks. The deformable tube is checked to ensure that this shock-absorbing feature is working well.

The bogies are also checked at Bishan Depot. Each train car has two bogies, and a six-car train has 12.

A dedicated bogie workshop inspects and tests the equipment to make sure it is structurally sound and can bear the weight of the train.

Ahead of the visit to Bishan Depot, reporters were invited to tag along on a rail replacement operation at Marina Bay station in the wee hours of the morning.

A crew of 13 to 14 workers was working to replace a chipped 18m rail segment about 400m away from the platform on the south-bound tracks towards Marina South Pier station.

This particular rail defect had been spotted by patrollers, who, working in pairs, walk 4km to 5km of tracks regularly to conduct visual checks of the rails.

Rail segments have to be replaced when they become defective or worn out over time.

SMRT evaluates all defects reported by patrollers or detected by ultrasonic inspections, and ranks them by severity and urgency.

The rail operator will then prioritise more urgent defects that require quick fixing, such as this chipped rail defect near Marina Bay station.

A total of around 60 workers do rail replacement works at six different locations, selected according to the severity of defects, from about 1.30am to 4.30am every day on the NSEWL, said SMRT.

SMRT general manager for track renewal Shazni Jaffar, 34, said the maintenance staff’s body clocks have to adjust to working the overnight shift.

“Of course, we have to make time for our families on our days off... The sacrifice is worth it because the work we do affects millions of people in Singapore as our rail network keeps the country going,” he added.

Also ensuring smooth train operations are some 600 train drivers at SMRT who operate the trains on the NSEWL.

These train captains are taught to handle 30 types of train faults, including signalling system and power faults. They are trained to respond to passengers who activate the emergency communication button while a train is running.

As a train captain, Ms Munirah Zulkepli can start her shift as early as around 4.30am to launch the first train into service, or end as late as 1.45am to return the train to the depot.

A total of 144 trains are launched on the NSEWL to maintain a two- to three-minute interval between trains during morning peak periods from 5am to 8.30am, said SMRT.

Having undergone 103 days of training before starting work as a train captain in the second half of 2023, the 29-year-old still finds her job exciting.

“Some passengers say ‘good morning’ – that’s kind of heartwarming, that they see us and greet us,” she said.

• Esther Loi is a journalist at The Straits Times, where she covers transport issues.
• Vanessa Paige Chelvan is a correspondent at The Straits Times. She writes about all things transport and pens the occasional commentary.

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