Minister for Transport Khaw Boon Wan stated in parliament that the operation control centre staff and the train captains, who were involved in the Joo Koon station incident, did not know that the protective bubble could be deactivated.
The minister was responding to questions filed by NCMP Dennis Tan Lip Fong who asked what were the control options available to the driver of the second train to stop the train before it collided into the rear of the first train, and what are the usual control options available to drivers of trains on North-South (NSL) and East-West Lines (EWL) for manual or emergency braking.
Mr Khaw said, "The cause of the collision was a software logic issue with a new signalling system. As a result the first train at Joo Koon station was operated without a protective bubble that ensures safe distances between trains."
"Tests have confirmed that the failure conditions must occur in a specific sequence for the protective bubble to be deactivated. Thales, the supplier of the system had not anticipated such a scenario. This was an isolated case with no precedent, even for Thales," he added.
The minister then said that if the operation control centre staff and the train captains had been aware of that they could deactivated the protective bubble, the train captain on the second train could have switched from automatic to restricted manual mode to drive the train manually or, as a last resort, engaged the emergency stop button to keep the train from moving.
"All North-South and East-West Lane, including those involved in Joo Koon station, are equipped with emergency stop buttons for the captains to apply the brakes manually. Based on train logs, the train captain in the second train was unable to engage these emergency brakes in time to avoid the collision," he said.
Mr Khaw then noted that Thales has since rectify the system to address the failure condition which led to the collision. In addition, Thales is setting up a simulation facility, a simulator, in Singapore to strengthen the testing process.
He then said, "We decided to separate the Tuas West extension from the rest of the EWL, which will continue until the rest of the EWL has fully transitioned to the new signalling system. Meanwhile, we are speeding up the re-signalling project and the extended engineering hours, from MRT early closures and late openings, will enables SMRT to complete this transition by the middle of this year."
Mr Tan then asked, "In ordinary circumstances, when the train is operated on automatic mode or controlled mode, what access does the driver or the OCC have to apply the emergency brake and what would be the expected reaction time?"
He also asked the minister, "Will SMRT be required to reviewed its SOP (standard operating procedure) processes in contingency situation like what we saw at Joo Koon, so that the driver will be alerted and be required to apply the brakes when the train start to move in unfeasible condition in order to prevent collision from happening?"
Responding to this, Mr Khaw stressed that this situation was never anticipated by Thales themselves.
He said "In hindsight, one can blame the captain, but I don’t. Because he was mentally not prepared and never trained to react for that kind of scenario."
The minister also said that based on the experts, the train operator could not react on time because you have to switch first from automatic to manual to have access to emergency brakes buttons.
The minister told Parliament a story about his friend who was not able to react on time, despite his friend was a responsible driver, saying that his friend collided with an e-scooter rider which caused the rider to pass away.
He then said that the question is, "Are you able to respond on time?"
Mr Khaw said that 36 metres is not a short distance, however, he noted that the train was travelling at 18 km/hour.
When asked by Mr Tan whether the train operator is able to access the emergency button when the train is travelling in an automatic system, Mr Khaw said that it might depend on the design. However, he said that he was not perfectly sure and said that he will check on the matter.