The Delhi Metro Rail Corporation is still trying to determine how a train door closed and the train began moving after a passenger's foot got stuck in one of its doors on Tuesday night, dragging him along to the next station.

The train that was in operation was immediately withdrawn from service and extensive tests are being conducted to determine how the incident occurred. “We are trying to recreate the incident through all kinds of simulations possible. As of now, I am not in a position to say how the incident occurred,” said DMRC Director (Rolling Stock) H. S. Anand on Thursday.

The mishap took place on Tuesday around 11 p.m. on a Line-3 train headed towards Rajiv Chowk from Dwarka. According to officials, the passenger tried to de-board the train at the last minute at Janakpuri West station. He almost stepped out of the train, but his ankle got stuck in the door as it closed. The man tried to pry the ankle loose with his hand, even as the train started moving. Passengers inside the train also held on to his hand for support, as he hung on to the train, getting off at the next station, Janakpuri East. The passenger was reported to be unhurt.

The doors on metro trains are equipped with sensors that can detect very small obstructions. “Whenever an obstruction of a dimension larger than 19 mm is encountered, the doors open up slightly. It tries to close in this way up to three times. If the obstruction still remains, the door remains open,” said Mr. Anand.

The DMRC has recently installed seven independent simulators at its Shastri Park Training Institute that replicate real time problems encountered by different sub-systems on a train, like brakes, air supply, door system, auxiliary system, traction system, train air-conditioning and train control management system.

At a press briefing at the training centre last Thursday, a DMRC engineer had explained that while train doors open automatically whenever they encounter an obstacle, the doors are also equipped with a “push back mechanism” that can be used to free small obstacles and prevent hold ups. “But the push back works only up to 50 mm of obstruction,” said Mr. Anand, adding as an example that someone's fingers or a purse string can be pried loose using push back.

“The CCTV footage shows that the lower part of the leg [of the passenger] above the ankle got stuck. We are trying to figure out why the train got power to move in spite of the obstruction. It should not have moved,” he added.

The spokesperson said that the passenger got off at Janakpuri East station, and has not pressed charges against the DMRC. While officials said that the man furnished his details to Delhi Metro officials, he “did not wait for any official inquiry or action and just walked away”.