In its latest update, LTA said the findings were that the first train departed Ulu Pandan Depot with the software protection feature, but the feature was inadvertently removed when the first train passed by a faulty signalling circuit.
“This train then arrived at Joo Koon station without the feature. The removal of this feature resulted in the first train giving off a train profile on the new signalling system of a three-car train, instead of a six-car train.
“As a result, the second train detected the first train as a three-car train and misjudged the distance between the two trains, therefore resulting in the collision,” it said.
LTA noted that Thales, the supplier of the signalling system, had confirmed the old and new signalling systems continued to be safe for operation.
LTA said the East-West Line was currently running on the old signalling system from Pasir Ris to Pioneer, and the new signalling system from Joo Koon to Tuas Link.
As a precautionary measure, trains would go through an additional layer of control measures and manual checks before they were deployed, it said.
“Operations from Joo Koon to Tuas Link will also be suspended tomorrow, Nov 16, 2017, while we conduct assurance checks with Thales. Bus bridging will be deployed for the affected stretch for the duration of the suspension,” added LTA.
According to LTA, about 8.18am today, a train heading in the direction of Tuas Link station stopped at Joo Koon station to detrain passengers due to an anomaly in the train signalling system.
At 8.19am, a second train stopped 10.7 metres behind the first stationary train.
“This is in accordance with the safety protocol of the signalling system protection that ensures safe stopping distance between two trains,” said LTA.
At 8.20am, after detrainment, the first train’s doors closed and before this train could move off, the second train, activated by the signalling system, moved towards the first train and hit it.
Thales, LTA and SMRT Corporation are investigating the incident.
The collision involving two trains today, was the second such incident in Singapore MRT’s 30-year history.