Oral Reply by Minister for Transport Khaw Boon Wan to Parliamentary Question on Joo Koon Collision

Mr Dennis Tan Lip Fong asked the Minister for Transport 

a.     in respect of the collision at Joo Koon station on 15 November 2017, 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

b.     what are the usual control options available to drivers of trains on North-South and East-West Lines for manual or emergency braking.

Mr Dennis Tan Lip Fong asked the Minister for Transport 

a.     before the collision at Joo Koon station on 15 November 2017, whether the operations control centre and the driver of the second train were aware that the protective bubbles of the first train had malfunctioned;

b.     if so, whether there were other options that could have been taken to ensure that the second train remained stationary; and 

c.     whether there was any previous occasion when a train had continued to operate when its protective bubbles had malfunctioned.

Reply by Minister for Transport Khaw Boon Wan:

1.     The cause of the collision was a software logic issue with the new Communications-Based Train Control, or CBTC, signalling system. As a result, the first train at Joo Koon station was operating without a protective bubble that ensures safe distances between trains. 

2.     Subsequent tests and re-enactments confirmed that the failure conditions must occur in a specific sequence for the protective bubble to be deactivated. Thales, the supplier of the CBTC system, had not anticipated such a scenario. This was an isolated case with no precedent, even for Thales. The Operations Control Centre staff and the train captains did not know that the protective bubble could be deactivated. Had they been aware of this, 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.

3.     All North-South and East-West Line trains, including those involved in the collision at Joo Koon station, are equipped with an emergency stop button for the train captain 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 avert a collision.

4.     Thales has since rectified the system to address the failure conditions which led to the collision. In addition, Thales is setting up a simulation facility, a simulator in Singapore to strengthen the testing process. The facility will enable LTA and SMRT to perform additional simulation tests in a controlled setting which is tailored to our local environment and the infrastructure conditions of our rail network before deploying on our train services. And as an added precautionary measure, we decided to separate the operations on the Tuas West extension from the rest of the East-West line. The separation will continue until the rest of the East-West Line has fully transitioned to the new signalling system. Meanwhile we are speeding up the resignalling project and the extended engineering hours from MRT early closures and late openings, will enable us to complete these transitions by the middle of this year.