The fallout from last week's train collision at Joo Koon station will echo for several more months. It will mean the end of seamless journeys for commuters travelling between Tuas and Pasir Ris on the East-West Line for at least up to June next year.
There will also be early closures along stretches of the East-West Line on Fridays and Saturdays, and late openings on Sundays from Dec 8 to 31 as resignalling works get speeded up to finish by June instead of the end of next year.
This will affect 17 stations from Tiong Bahru to Tuas Link, as well as Bukit Batok and Bukit Gombak stations on the North-South Line.
On Dec 10 and 17, which are Sundays, these stretches will also close for the whole day.
The changes were flagged after it was revealed that the collision was caused by compatibility issues between an old and a new signalling system. To avoid the risk of a repeat incident, the two systems will remain separated till next June.
That means commuters travelling between Tuas and Pasir Ris on the East-West Line will not have a seamless journey for a while. They will have to get off at Joo Koon and take a free bridging bus service to the next stop at Gul Circle, to continue westwards on a line which runs on the new signalling system.
Likewise, on the return trip, they will have to get off at Gul Circle and take the bridging bus service to Joo Koon to continue eastwards.
Stony-faced representatives from SMRT, regulator Land Transport Authority (LTA) and signalling system provider Thales met the media yesterday to reveal their findings on the Nov 15 collision which left 38 people injured. Thales official Millar Crawford said: "We apologise to commuters, in particular to those who were injured."
Speaking to reporters after the briefing, Transport Minister Khaw Boon Wan said: "When we launched Tuas West Extension, we intended it to be a seamless link from Pasir Ris to Tuas Link. In hindsight, of course, this has introduced a lot of complications... Still, Thales could have done better."
It has been decided to have "complete separation" between the old and new signalling systems. The old system was originally to be phased out by the end of next year. But to minimise impact on commuters, it is now targeted to end by June.
Meanwhile, the shortened service hours from Dec 8 to Dec 31 will affect 20,000 to 30,000 people, the LTA said, adding that other stretches of the East-West Line will see reduced service hours in the first half of next year too.
The briefing on the Nov 15 incident revealed that a glitch on trainborne signalling equipment disabled a "bubble" which acts like an invisible barrier to prevent trains from colliding. The system then created another bubble.
But the second bubble was disabled when the train passed Clementi station. A trackside device which was modified two days earlier to connect the two signalling systems failed, resulting in compatibility issues between train and track.
At Joo Koon, this train which no longer had the protection of the bubble - rendering it almost invisible to other trains - was hit by another.
Mr Khaw said the collision - as well as the flooding incident - have "shattered" the confidence of commuters. "But it has happened, and we have to get over it and regain the public's confidence." Upping the reliability of the whole system would be key to this end, he said.