Half a dozen track circuit-related delays, on the Clementi-Joo Koon stretch of the line, have occurred in the past one and a half months alone. The most serious delays were on 23rd, 19th and 4th January, when train services were disrupted for four hours, two and a half hours and one hour, respectively. The most recent incident was on Sunday.
SMRT said most of the incidents - which took place during peak hours - were traced to faulty track circuits, which help to keep trains at a safe distance from each other. But the rail operator could not say why it has not been able to resolve the repeated glitches nor cite a cause other than the age of the line, which is close to 30-years old.
The Straits Times understands that there were times when technicians sent to fix a circuit fault would get a 'no fault' reading on their diagnostic equipment. SMRT suggested in its reply that the glitches - reminiscent of the signalling faults which bedevilled the Circle Line in August, September and November last year - would go away once the signalling system is upgraded next year.
"There are more than a thousand track circuits on the North-South and East-West Lines (NSEWL)... As a safety precaution, trains within the faulty track circuit would be required to be driven manually and at a slower speed. This, in turn, could cause trains behind to slow down," said a spokesman. This causes congestion, especially during peak hours, when trains are travelling closer to one another.
"We are working on replacing all track circuits as part of a resignalling project. In addition, the new signalling system, being more advanced than the current system, which was installed 30 years ago, will be more reliable as it is built with multiple redundancies." SMRT had also said the disruptions were not related to the recently installed sleepers. The four-year project to upgrade sleepers on the NSEWL, from older timber sleepers to hardier concrete ones, was completed last month. It was supposed to bring smoother and safer rides.
