A track fault on the East-West Line affected thousands of morning peak commuters yesterday as MRT trains crawled haltingly between Boon Lay and Clementi.
The incident - traced to a track circuit glitch between Jurong East and Clementi stations - caused delays from around 7.30am to 10am.
There have been at least two other track faults along this stretch during the morning peak since the year started.
Operator SMRT alerted the public on Twitter of the fault at around 7.30am, saying that east-bound journeys would be 10 minutes longer.
Later, it raised the estimated delay to 15 minutes, and then 20 minutes.
At about 9.20am, it tweeted to say the fault had been resolved, but train service took another hour or so to return to its usual speed and frequency.
Stockbroker Cole Cheong, 50, who takes the train from Boon Lay to his workplace in Raffles Place, said at 9.13am: "Thirty minutes already and still have not reached Clementi (four stops away)."
He was 55 minutes late for work.
Marketing and communications manager Eugene Mok, 31, said he was half an hour late for work yesterday.
"The journey from Lakeside to Jurong East (two stops) took half an hour," he said. "Usually it takes five to six minutes."
He said he missed his shuttle bus, and had to take a cab to complete his journey.
"This has been happening almost weekly," he noted. "Last week, there was a five- to 10-minute delay along the same stretch.
"And on Jan 3, there was a 15- to 20-minute delay, also on the same stretch. It was the first day of my new job, and I was nearly late."
SMRT tweeted the Jan 3 incident, attributing it to a track fault.
Mr Mok said: "They need to get their act together and find out what's behind the recurring delays."
He added that while the five- to 10-minute delay may seem minor, "it's not so simple".
"During peak, even a five-minute delay will cause a huge build-up of passengers down the line," he said.
Yesterday's incident came a week after the Transport Ministry announced on Jan 12 that rail reliability had improved by 30 per cent last year.
Trains travelled an average of 174,000km before encountering delays of more than five minutes, up from 133,000km the previous year.
A major contributor to the improvement was the new Downtown Line, which clocked a record of over one million km without a single fault in the third quarter - five times better than the 209,000km average of the other three quarters.