MRT trains are designed in such a way that when any one door is not closed properly, the train cannot move off. This is because the electrical circuitry of the doors is interlocked with an electrical system that controls the train propulsion system. But if a door's electrical circuitry is isolated from the train propulsion system, the train can move when the door is open. Technical faults or human error can also lead to a train moving when a carriage door is open, as it did on Monday.
Responding to a query, SMRT Trains Chief Executive Lee Ling Wee said, "The station manager made an error in bypassing the train door interlocking system before the train door was closed. This allowed the train to move off. We are strengthening our procedures to prevent a reoccurrence of such nature. Safety is our top priority."
Former SMRT Trains employees said it should not have happened, but it sometimes does. One former veteran SMRT operations staff member explained, "When there's a problem with one of the doors, the train will not be able to move. Someone will need to activate a door bypass switch and withdraw the train from service." He said Monday's incident was 'definitely human error'. The Straits Times understands that the train involved, procured and owned by the Land Transport Authority, was put into service two years ago.
In 2016, an LRT train door opened while the train was travelling from Bukit Panjang to Senja amid a five-hour service disruption. SMRT said then that the cause could have been a design flaw. Singapore Institute of Technology Associate Professor Andrew Ng said, "Based on the interlocking principles, the train should not move until all doors are closed and locked. However, the operator can intervene and override the interlocking, causing the train to move." University student Kyle Malinda-White, 26, said, "Our system is not that old. They should fix it."
