SINGAPORE - Disruptions on the East-West MRT line earlier this month were caused by faulty track circuits and were unrelated to the replacement of sleepers on the ageing line, said rail operator SMRT on its blog on Sunday (Jan 29).
The four-year project to upgrade sleepers on the 30-year-old North-South and East-West lines was completed last month.
Train services on the East-West line were disrupted twice in the past two weeks - once on Jan 19 during the morning peak period and again last Monday (Jan 23) evening - due to track circuit failures between the Jurong East and Clementi stations.
There was also a track fault near the Clementi station on Jan 4, which caused a delay of an hour during the morning peak period.
Track circuits are integral to the signalling system, said SMRT, as they send signals to the operations control centre to monitor the speed, location and identity of trains.
"When a track circuit fails, trains have to travel at a lower speed over the affected stretch for safety reasons," said the rail operator, adding that the slower speeds of trains caused congestion during peak hours.
SMRT said that track circuit failure could be caused by an equipment failure either at a signal equipment room within an MRT station or at track side.
While a hardware failure in the signal equipment room can be quickly rectified, for trackside failures engineering staff must go down to the track to investigate the cause.
The transport operator said that this can be "very challenging" when the track is on a rail viaduct, particularly in cases of heavy rain or lightning risks.
Replacement of the signalling system, which began in 2012, will substitute the old track circuits with a "more advanced system that is more reliable", said SMRT.
"After we renew the signalling system, faulty track circuits will no longer cause prolonged delays for commuters."
More than 85 per cent of signalling upgrading works on the East-West line have been completed, and the new signalling system is expected to be operational by the end of next year.
The new system is also expected to increase train frequency as it will allow trains to run at intervals of 100 seconds, instead of 120 seconds now.
Earlier this month, the Land Transport Authority said that the new signalling system on the North-South line will begin operating in March this year during the off-peak periods.
In a blog post last month, SMRT Trains managing director Lee Ling Wee said that a third of train delays that lasted more than five minutes last year on the East-West and North-South lines were signal-related.