SINGAPORE: The “inadvertent” disabling of a software protection feature has been identified by the authorities as the reason for an SMRT train hitting another, stalled train at Joo Koon station on Wednesday morning (Nov 15).
Thirty-six people were injured after a train “moved forward unexpectedly” and “came into contact” with another stationary one in front of it, according to earlier statements from the Land Transport Authority (LTA) and SMRT.
At a joint press conference held later Wednesday, LTA deputy chief executive of infrastructure and development Chua Chong Kheng said preliminary findings indicated that the first train - in front - departed Ulu Pandan with a software protection feature which was “inadvertently removed” when it passed a faulty signaling circuit.
“This train then arrived at Joo Koon station without the feature,” said Mr Chua. “This resulted in it giving off a train profile on the new signaling system of a three-car train instead of a six-car train.”
“As a result, the second train (behind) detected the first train as a three-car train and misjudged the distance between the two, causing a collision.”
Mr Chua said that as a precaution, operations from Joo Koon to Tuas Link will be suspended for the entire day on Nov 16 while assurance checks are conducted with signaling contractor Thales.
Bus bridging will be deployed for the affected stretch for the duration of the suspension.
Trains will also go through an additional layer of control measures and manual checks before they are deployed.
These include instructing drivers to be more alert and vigilant, even when their trains are in automated mode, said Mr Alvin Kek, SMRT Trains’ senior vice president of rail operations for the North-South and East-West Lines (NSEWL).
He said the rail operator would also increase the timed separation of trains arriving at NSEWL stations - up to between 2.5 and three minutes from the present two - until they were satisfied with findings from the ongoing investigation.
Expanding on his use of the word “inadvertent”, Mr Chua said there was no indication that the removal of the software protection feature was due to human action.
"The new trackside signaling circuit is still a work-in-progress and as the train passed by, we observed this (software protection) feature got removed,” he said, adding that a thorough investigation was being conducted to get to the root cause.
Mr Chua said that when the first train stalled at the station - due to an anomaly in the train signalling system - station staff boarded the train to run checks, and safety protocol at the station closed down the track to “physically protect” another train from coming in.
When the second train arrived, it “observed this stopping point” by halting 10.7m behind the first - a safe stopping distance, said Mr Chua.
Authorities were asked if the rear train driver - subsequently injured in the collision - could have overrode the signalling system and prevented his train from moving forward at an estimated speed of 16kmh.
Said Mr Kek: “10.7 metres away is relatively close, the movement before coming into contact with the first train took only 10 seconds.”
When asked if the train driver can override the signalling system, Mr Kek said:“There are systems in the cab where he can request to apply brakes.”
Responding to a follow-on question if the driver applied the brakes, Mr Kek said: “That is what we are investigating now.”
Meanwhile, Thales representative Peter Tawn said this was the first incident of such a nature.
“We are very confident our system is safe,” he reiterated. “The Thales system is on record one of the safest there is ... We’ve never had a collision.”
Said Mr Chua: “Obviously the situation is not satisfactory, we are concerned and will work closely with SMRT on this.
“There’s also a technical bit here and we must be clear about responsibilities. This incident involve technical aspects and we need to iron those out with Thales.”
“But ensuring the safety of our commuters remains our priority,” he insisted.
Thales is the French company which supplied the new signalling system.
3 INJURED PASSENGERS WARDED
One of the trains involved in the incident was pulled away in the direction of Tuas Link MRT station at about 3.20pm. The second train was moved out about 4.05pm.
Of the 29 injured, 23 passengers and two SMRT staff sustained "light to moderate injuries", and were taken from the scene of the incident to Ng Teng Fong Hospital and National University Hospital (NUH) in the morning.
Ng Teng Fong General Hospital received four additional walk-in patients later in the day.
Three patients remain warded for observation - two at Ng Teng Fong General Hospital and one at National University Hospital.
In all, 24 patients received treatment and were discharged, one declined treatment and returned home and one is still being treated.
The last time an MRT train collision happened in Singapore was more than two decades ago. That incident - a front-to-back collision between two trains at Clementi station on Aug 5, 1993 - resulted in 156 injured commuters.
An independent inquiry panel found that the accident was caused by a 50L oil spill from a maintenance locomotive which had been carrying out maintenance work at about 5am on the day of the accident.
Watch the press conference in full: