An AC Metro train with passengers on board ran its full stretch from Dum Dum to Kavi Subhash (New Garia) with one of its doors wide open on Wednesday morning.

Metro’s insurance against any possible accident — a Railway Protection Force jawan and an employee to man the gate and “supervise passengers” on the entire stretch.

The train started from Dum Dum around 10.40am, after the motorman and the guard tried in vain for 15 minutes to manually close the door in the fifth coach. After completing its 27km journey, the train was taken to the depot at New Garia. It did not make any more trips for the day, a Metro official said.

According to the safety checks in place, a Metro is not supposed to start unless all doors close. The Metro official said the affected door was “isolated from the system” to start the train.

A damaged nylon strip at the bottom channel of the door led to the snag, another official said. “Prima facie, the snag was not a design fault but occurred because of lack of maintenance.”

Maintenance of rakes, some of which are three decades old, has been a problem for long. Officials have said in the past that fewer rakes led infrequent maintenance. “Rakes were used for longer periods. Now, conditions have improved... but maintenance is still an issue because of lack of infrastructure,” the official said.

The authorities’ decision to run the train instead of stopping it or vacating the coach or at least stopping passengers from using the door has triggered questions.

Officials, though, said it was a “conscious decision” to run the train in view of the rush hour.

“The train arrived at the platform at 10.24am. There was heavy pressure of passengers and multiple trains were lined up behind the train. It would have taken a lot of time to clear the line and take the train back to the Noapara depot. We could not have afforded any further delay,” Metro spokesperson Indrani Banerjee said.

The affected door was to the left of the coach and most platforms en route are to the right. But at Park Street, Tollygunge and beyond, the platform for Kavi Subhash-bound trains are to the left and passengers got on and off the train through the door, which remained open.

“It was like travelling on a local train, especially after Tollygunge. The coach was so breezy,” a passenger who boarded at Esplanade and got off at Garia Bazar said. Trains run on a viaduct between Tollygunge and New Garia.

The average speed of a Metro train is under 40kmph. “The train started moving without any announcement about the door. There was no announcement for the rest of the trip,” Ranjan Niyogi, a Birati resident who was in the fifth coach, said. Niyogi took the train at Dum Dum and got off at Esplanade.

Asked if vacating the coach or cordoning off the door would have been a safer option, an official said it was not feasible because of the “heavy load of passengers”. “Past incidents have shown that passengers are not ready to budge during rush hour,” he said.

A preliminary check has pointed to a damaged nylon strip at the bottom channel of the door.

“The nylon strip snapped because of passenger thrust on the door leaves. The last time the door opened, the damaged strip got further entangled with the metal and did not let the door close,” an official said.

Metro trains running with open doors is not exclusive to Calcutta. In September 2017, a packed Metro in Delhi travelled two stations in the Yellow Line with one of its doors open. The train operator was suspended for safety lapse.