According to News18, Kolkata's East West Metro, which is approximately 16.6 km long, will ferry an estimated 1 million people per day by 2035.
The project that is expected to be complete by 2021, will also feature India's first ever underwater tunnel.
The 520-metre twin tunnel, one east-bound and the other west-bound, has been built 30 metres below the riverbed, which means commuters will be underwater for close to a minute.
This will happen when the train they board passes between Howrah and Mahakaran metro stations, reports News18.
The 5-km stretch between Salt Lake & Howrah was inspected on Tuesday, July 23 and is expected to be operational soon.