Software glitch caused second train to misjudge distance: SMRT
A faulty signalling circuit had disabled a software protection feature that would have prevented the accident between two SMRT trains yesterday morning.
The collision occurred at around 8.20am at Joo Koon station, injuring 29 people after a packed train hit a stalled train from behind.
Land Transport Authority (LTA) and SMRT officials told a press conference yesterday evening that preliminary findings had revealed that though the stalled train had a software protection feature, it "was inadvertently removed" when the train passed by a faulty signalling circuit.
As a result, the first train was observed as a three-car train instead of six, causing the second train to hit it after it misjudged the distance between them.
The trains were 10.7m apart, which LTA says is in accordance with safety protocol.
The lowest distance between trains is 10m while the farthest is 50m depending on the speeds of the trains.
The second train was travelling at an estimated 16kmh when the accident occurred.
By then, the passengers in the first train had disembarked after it stalled at Joo Koon following an anomaly in the train signalling system.
Twenty-seven of the second train's 517 passengers were taken to hospitals as well as one SMRT employee each on board the first and second trains.
Describing yesterday as an "awful day", Transport Minister Khaw Boon Wan apologised to commuters for the injuries and inconvenience.
Asked if a committee of inquiry would be convened to look into the incident, Mr Khaw said the investigation should be allowed to take its course.
As for how this will affect commuters' confidence in the MRT system, he said: "Obviously people will be upset... I'm equally upset."
Signalling provider Thales said this is the first time such an incident has occurred with its signalling system.
Thales added that both the old and new signalling systems are safe for operation. The site of the collision is using the new system.
Train services between Joo Koon and Tuas Link will be suspended today for checks.
Bus bridging services will be provided.
Interim control measures have been implemented, with the distance between trains increased for now during investigations. Commuters should expect longer waiting times between train arrivals.