Further investigations conducted on a segment of the East-West line, following the train collision at Joo Koon station yesterday, have revealed that the software glitch that caused the two trains to collide arose because the faulty train was “transiting between the old and new signalling systems.”
This is according to Land Transport Authority (LTA)’s latest statement on the matter, late this evening, in which it said:
“Given this finding, LTA and SMRT have decided to isolate for up to one month the operations of the Tuas West Extension, which runs on the new signalling system, from the rest of the East-West Line, which runs on the old signalling system. This will enable our engineers to carry out further assurance checks together with Thales.”
In a separate statement, Transport Minister Khaw Boon Wan said that he was “disturbed” that a “critical safety software could be disabled by a defective trackside device.”
Asserting that the link between the Tuas West Extension and the rest of the East-West Line should not be resumed until this issue has been fully addressed, the Minister added:
“I have told the team to keep separating the two sections of EWL, if need be until the entire EWL is ready to run on the new signalling system,” he said. “This way we avoid having trains transiting from one signalling system to another with its attendant safety risk.”
We re-publish LTA’s latest statement here in full:
“The whole-day suspension of the Tuas West Extension service on 16 November 2017 has been very useful for the Thales engineers to carry out detailed assurance checks on the new signalling system.
Based on these checks, Thales has confirmed that the old and new signalling systems are respectively safe for operation.
The disabling of the software protection feature that resulted in the 15 November 2017 train collision arose when the faulty train was transiting between the old and new signalling systems.
Given this finding, LTA and SMRT have decided to isolate for up to one month the operations of the Tuas West Extension, which runs on the new signalling system, from the rest of the East-West Line, which runs on the old signalling system. This will enable our engineers to carry out further assurance checks together with Thales.
As we need some time to prepare our commuters and our staff for this arrangement, the suspension of Tuas West Extension will continue till Sunday.
Train service on the Tuas West Extension between Gul Circle and Tuas Link will resume operations on Monday, 20 November 2017, using the new signalling system.
The rest of the East-West Line will continue to run on the old signalling system between Pasir Ris and Joo Koon.
From Monday, when the Tuas West Extension resumes service, bridging bus services will be available between Joo Koon and Gul Circle MRT stations (see Annex).
This morning, 33 buses were deployed on the bridging bus service between Joo Koon and Tuas Link MRT stations at headways of three to five minutes.
In addition, several bus trips were added to key trunk services in Tuas to better serve commuters in the area. Service was satisfactory.
We will continue to provide bridging bus services between Joo Koon and Tuas Link MRT stations until Sunday evening.
LTA and SMRT will continue to investigate the incident together with Thales.”