Metro sources said the trains and the stations were ready for resumption of commercial service but enforcing social distancing norms would be a real challenge.

“There is no mechanism to ensure social distancing without physical intervention. It will be premature to say anything on our preparedness before the guidelines come. But we might have to depute security personnel inside coaches,” said a Metro official.

Only a set of trains in the Metro fleet has CCTV cameras inside coaches. Live feed can only be accessed by the motormen. There are cameras at stations but not enough to track the number of passengers entering the concourse and the platform. Since the control room cannot access the live footage, there cannot be any instant direction to seal the gates of a train or platform, said officials.

“Let us say the central guidelines allow 50 passengers per coach and 40 passengers board one on a New Garia-bound train from Dum Dum. How do we restrict the number in the subsequent stations?” said a Metro official.

Keeping track of the number of passengers will be challenging because of the multiple origin and destination points. There are 24 stations on the route.

“Once commercial service starts, tokens will be suspended. Only smartcard-users will be able to use the services. They can recharge the cards at the counters or from the Metro Railway website. An app for the smartcard-users is in the works,” Metro spokesperson Indrani Banerjee said.

But the carrier is not equipped to keep real-time track of the number of smartcards swiped at each gate.

It is expected that passengers will have to undergo thermal screening before entering the stations. The Metro authorities will need police’s help in conducting the checks. “We will need police help in planning anything, both outside and inside the stations,” said another official.

Metro’s security is the responsibility of the Railway Protection Force. But the RPF’s Metro contingent is working with a curtailed workforce. “The sanctioned strength is 900. We have a shortfall of around 130,” said an RPF official.

RPF sources said the crunch was more acute because over 50 from the existing team have been sent to East-West Metro, which, once fully operational, will link Salt Lake Sector V with Howrah.

On the table are options of closing the shutters at stations the moment the volume of passengers goes up, said officials. “We are used to doing it during the Puja rush. The permissible limit will be more at the terminal stations than the intermediate ones,” said an official.

To counter the threat of transmission of the Covid-19 virus in an enclosed air-conditioning system, the quantum of fresh air will be increased on trains, said an official.

“We will raise the supply of fresh air to the maximum level so that the existing air is not recirculated,” the official said.

The frequent touch points like railings and handlebars will also be sanitised frequently once the services start, said the official.

Sanitiser dispensing machines were installed at some Metro stations on Sunday. “All stations will be covered within a couple of days,” the official said.