Thousands of commuters were affected after a track circuit fault caused trains to slow down and stall intermittently on the North- South Line for two hours during the morning rush hour yesterday.
Republic Polytechnic (RP) second-year student Brian Lee, 19, missed his exams as a result. He said the train he took stopped for 15 minutes between the Jurong East and Choa Chu Kang stations, and again for 25 minutes as it headed towards Kranji.
"Students living in the West who are studying at RP were affected as it was our mid-year exam period," he said.
SMRT said the fault between the Woodlands and Admiralty stations resulted in trains slowing down in both directions from 7.21am yesterday.
By the time service resumed two hours later, at around 9.25am, congestion had built up at several MRT stations.
At the Yishun and Ang Mo Kio stations, for example, passengers said the escalators were shut down temporarily to slow down the inflow of commuters after the platforms became crowded.
"To help ease congestion and ensure passenger safety, station staff carefully managed the flow of commuters through the fare gates at stations between Yew Tee and Ang Mo Kio," said Mr Patrick Nathan, vice-president of corporate information and communications at SMRT.
Free shuttle bus services were offered to commuters from Yew Tee to Toa Payoh and Ang Mo Kio. SMRT said in a Twitter post that commuters could expect journeys to be delayed for up to 25 minutes.
An RP spokesman said "a small number" of students missed the exams. He said those who arrived within a 30-minute "grace period" could still take the exams. Those arriving more than half an hour after the start time would be evaluated on a case-by-case basis, he added.
Financial consultant Andy Heng, 26, was at least half an hour late for work. He got off the train in Sembawang to join the taxi queue because the train was "moving too slowly".
"Breakdowns have been happening so often despite frequent maintenance, so I think it's time the operators tried something different," he said.
There have been at least 15 rail disruptions or delays since the start of the year, including those on the LRT system. The number of major breakdowns - those lasting more than half an hour - hit a four-year high of 12 last year.
The Kranji-Yew Tee stretch is the most problematic section of the North-South Line. At least seven breakdowns this year arose from faults there.
Public relations officer Oun Hui Peng, 39, was not affected by the delay but was concerned. "These faults happen frequently at the same section," she said.
These longstanding issues may be understood better when experts give the rail network a thorough check. In late April, the authorities called for tenders inviting parties to analyse the condition of the operating system and to examine the infrastructure.
Contacted yesterday, Mr Cedric Foo, chairman of the Government Parliamentary Committee for Transport, said transport operators need to ensure that services are reinstated and commuters get to their destinations quickly when track faults occur.
"Given that it took place during peak hours, many commuters would have been inconvenienced as they needed to get to work, and clearly more attention needs to be paid to this," he said.
The Land Transport Authority said it is investigating the incident.