SMRT explained that “all Circle Line trains have a built-in feature which allows a door to open up to 5cm when someone exerts force against it, creating a maximum gap of 10cm if both doors are prised open.”
Still, concerns continue to be raised as at least two more similar incidences have taken place, one in December and another in January this year.
Ms Tan Sock Hua was travelling on the train with a friend in December last year, during the peak hours of between 6pm to 7pm. As the train was moving, a gap of about 15cm opened up between the train doors. Ms Tan quickly grabbed her friend, who had her back towards the door, when she saw this.
She was so upset by the experience, and the potential consequences of it, that she wrote to the SMRT for an explanation.
“We have thoroughly investigated the matter and conducted fleet wide checks on our train doors but did not find any abnormality,” the SMRT told her.
“However, we suspect that the gap between the doors was due to the ‘push-back’ mechanism,” it explained. “The doors are also designed with a ‘push-back’ mechanism, which allows passengers to push the doors open to create a maximum gap of 10cm if they need to free thin objects, such as bag straps or clothing, caught in the doors. In this instance, we suspect that the ‘push-back’ mechanism was being pushed open accidentally, hence the gap was visible.”
The SMRT added that the Circle Line has “many fail-safe features to ensure passenger safety.”
“For example, the Door Interlock Relay, which is a system available on all modern railway lines, ensure that trains will not be able to move off if the train doors are not properly closed. In addition, the doors of the Circle Line trains are built with mechanical latches that prevent any doors from being forced opened beyond 10cm.”
However, Ms Tan questions why the doors are allowed to open while the train is moving, even if its purpose is, as SMRT says, to allow objects caught between the doors to be freed.
“What we find hard to agree is that this auto door mechanism for small trapped stuff like handbag straps getting caught is activated when the train is off running at fast speed inside tunnel,” Ms Tan says. She feels that the doors should only be allowed to open when the train is in the station and not when it is moving.
On 8 January, another incident of the train doors opening while the train was moving was reported by a commuter. The SMRT, in its response to the incident, said “train doors are designed to open slightly when pressure is applied to them.” It also repeated its earlier explanation of why the doors would open and added that “the Door Interlock Relay, which is a system available on all modern railway lines, ensure that trains will not be able to move off if the train doors are not properly closed.”
Still, commuters like Ms Tan is not entirely convinced and says she will exercise more caution when taking the train. “Yes, I'm definitely more cautious standing next to the doors now because of the fact that the problem has not been fixed. There's always a possibility of a freak accident.”
“We would like to remind passengers not to lean against the train doors,” the SMRT said, “as this may cause the ‘push back’ mechanism to work while the train is on the move."