An adjustment in operations to alleviate delays and interruptions on the Metro Blue Line has been effective, though only to some degree.

There was a another disruption on the Blue Line on Sunday night, the latest in a series of glitches. It was triggered by a snag in a Dakshineswar-bound train just as it entered Tollygunge. Services were suspended between Maidan and Shahid Khudiram from 6.45pm. Full services between Dakshineswar and Shahid Khudiram resumed at 7.50pm, the carrier said.

Last week, a resident of south Calcutta entered Chandni Chowk station after 9pm. He had to wait for 20 minutes before he got a train to Kalighat.

On Saturday, a regular Metro passenger entered Esplanade station around 4.30pm. The man was headed to Masterda Surya Sen (Bansdroni). “The display board showed an arrival time of 4.33pm. But the train arrived 10 minutes later,” said the man.

Metro services on the Blue Line were disrupted for three hours earlier on Saturday due to a signalling problem at Dum Dum

“The period after the New Garia station closure was horrible. The situation has improved since then, but Metro is still far from what it was. Delays are still common. Every second day, there is one technical problem or another,” said a woman who travels between Tollygunge and Central on an almost daily basis.

Ever since commercial operations were suspended at Kavi Subhash (New Garia) station on July 28 following cracks in the platform pillars, the north-south corridor has been under tremendous pressure. Delays and disruptions assumed a gigantic scale in the immediate aftermath of the suspension of operations at the southern terminal of the city’s most popular Metro link.

Blue Line trains are now being terminated at Shahid Khudiram (Briji) in the
south. But it lacks infrastructure commensurate with a terminal station. The longer turnaround time needed for a train to switch direction from south to north had a cascading effect on the entire corridor.

In the second week of September, the carrier introduced a tweak. Several trains headed south were terminated at Mahanayak Uttam Kumar (Tollygunge) station before they began their northward journey.

For a considerable time, Tollygunge functioned as the southern terminal and possessed ample resources for trains to switch their directions.

The scale of the problem dipped after the tweak, but it is far from over.

“An empty train is still switching tracks at New Garia station, but not at the usual place. A single switch is taking around 10 minutes, double the usual time. At the northern terminal at Dakshineswar, trains can switch directions in five minutes. The extra time used in the south is having a cascading effect on the whole corridor. Metro trains run in a loop. Ideally, the turnaround time should be synchronised at both ends. The difference of five minutes is impossible to discount,” said a Metro official.

One in every three trains is now being reversed at Tollygunge during peak hours, and one in every four in non-peak hours.

“Without this tweak, things would have been much worse,” the official said.

The ageing infrastructure of the Blue Line, which became operational in the 1980s, is also stretching the carrier.

The signalling system, the tracks, and the tunnels are more than four decades old. As they depreciate, snags will be inevitable, officials said.

The Blue Line needs a complete overhaul, for which the carrier has set the ball rolling. But when it will start has not yet been decided.

The carrier is set to install a new rake reversal point at Shahid Khudiram. A weekend traffic block will be needed to finish the work. Sources said it was likely to take place over the weekend after Diwali.

“The reversal point will reduce the turnaround time. But it will still not be as smooth as it was at New Garia,” said one of them.

A raze and rebuild job at Garia, set to take at least six to seven months, is expected to begin in a fortnight, after the new reversal point is ready.