A fault in a track point disrupted rush-hour services on the East-West Line yesterday morning, causing thousands of MRT commuters to face delays of up to 40 minutes.
It was the second disruption on the line in two days. On Tuesday morning, EWL services were affected by a faulty platform screen door.
Among the five delays SMRT has tweeted about since last month, four pertained to the EWL. The fifth involved the Circle Line.
In a statement yesterday evening, SMRT said that after examining the fault, its staff assessed that train operations could continue, but at a slower speed.
A decision was then made to keep the trains running during the morning peak period and work on the faulty point machine - which is used to control train movements at rail junctions when trains move from one track to another - only after the morning rush hour.
"This would allow EWL commuters to travel from Jurong East towards the city, and commuters to travel from the city to the interchange station at Jurong East," the statement added.
"After the morning peak, engineering staff went down to the track in between service and fixed the point machine at 1.20pm," it said.
"This arrangement required EWL trains at Jurong East and Clementi to halt temporarily for up to five minutes every time the engineering staff went on track to carry out repair work. The team accessed the track six times. After the fault was rectified, train services returned progressively to normal speed."
Trains kept going to lessen impact: Janil
A decision could have been made to stop the train service to fix a switch mechanism problem that caused delays on the East-West Line yesterday, said Senior Minister of State for Transport Janil Puthucheary.
But this would have had a "very big impact on the commuter experience", he told reporters on the sidelines of the launch of the SG Mobility Gallery.
He said the eventual decision to keep trains moving meant the service was slowed down, causing delays of up to 40 minutes for commuters during rush hour.
Dr Janil added: "We thought, on balance, that was better for the commuters, but it does mean that it is going to take a little bit of time to ascertain exactly what the problem is with the switch mechanism."
He was speaking to reporters before SMRT tweeted that it had rectified the fault.
SMRT first tweeted about the latest delay at 7.10am yesterday.
In a Facebook post at 8.45am, it said train services had to be stopped between Clementi and Jurong East stations to allow its technicians to go onto the track to check on the fault.
"Due to slow train movements, please cater for additional 40 minutes of train travel time. We are sorry your morning commute has been affected," the post added.
At 2pm, seven hours after the incident, SMRT announced on Facebook that regular service had resumed.
SMRT did not explain what caused yesterday's fault, but observers believe it could be linked to a maintenance lapse or failure to spot and replace worn components.
The Straits Times understands that trains were unable to change tracks because of the fault, and the changeover had to be done manually. Because of safety and other considerations, there was a slowdown in the process, which normally would take seconds.
But not all trains were affected yesterday, even though commuters in the eastern part experienced slower services intermittently.
SMRT said that free regular bus services and bridging bus services were made available between Boon Lay and Queenstown. These ceased by 2pm.
It also added that to ease congestion while the fault was being fixed in the morning, it sent four additional trains to pick up commuters travelling towards the city from Jurong East and another two trains to Clementi to serve commuters headed to the city.
Commuters affected yesterday included Ms June Lim, 29, who works part-time at a retail store in City Square Mall.
"I have been stuck in the train for quite long. It took me 45 minutes just to get to Clementi from Boon Lay, when usually it would take just 10 minutes," she said. "It was so humid that I felt faint."
Mr Adam Haddis, 64, an administrative support worker in the oil and gas industry, said he left his Woodlands home at about 8am, and it took him 1½ hours to get to work in Boon Lay. The journey would usually take him an hour.
"If I had known about the fault, I would have taken the bus," he said.
• Additional reporting by Ng Huiwen and Gilaine Ng