Life under the river: How the east–west metro is redrawing Kolkata’s daily map

KOLKATA: Imagine slipping beneath a great river in the comfort of an air-conditioned metro cutting hours of travel into minutes and reshaping the daily rhythm of a city. This is now part of everyday life in Kolkata thanks to the East–West Metro, the city’s second metro line, also known as the Green Line. The city’s first metro, the North–South corridor (Blue Line), opened in October 1984, making Kolkata the first Indian city to have a metro, a title it held until Delhi Metro launched its first line in 2002.

A new passage under a historic river

The East–West Metro runs 17 km from Sector V in Salt Lake on the east to Howrah Maidan on the west bank of the Hooghly River. A key feature of this line is its underwater tunnel: a 520-metre stretch beneath the river, India’s first transport tunnel of its kind.




Trains run about 16 metres below the riverbed, while the Howrah station on this route is now India’s deepest, built around 30 metres underground.

The metro has transformed commuting for lakhs of residents between Salt Lake and Howrah, as well as hundreds of thousands from the suburbs who access the service via Howrah and Sealdah railway stations two of the busiest in India, serving nearly 20 lakh passengers daily.

Engineering against the odds

Construction of the Green Line stretched over more than a decade. River tunnelling was completed in a record 67 days in 2017. Engineers had to dig through soft, unpredictable alluvial soil and build waterproof tunnel linings designed to last over 120 years.

Central Kolkata, particularly Bowbazar, posed significant challenges. Ground subsidence and water ingress disrupted tunnelling, delaying parts of the project for years before the river crossing could be completed. The twin tunnels were excavated using earth pressure balancing tunnel boring machines, cutting through predominantly stiff clayey silt beneath the riverbed.

Interestingly, the underwater tunnel is not a new idea. Sir Harley Dalrymple-Hay, a Birbhum-born British engineer, drafted plans for an underwater railway in Kolkata as far back as 1921.

From trials to daily routine

After years of construction and testing, the East–West Metro opened for commercial service in March 2024. Thousands of commuters boarded the first trains with excitement as the Green Line began stitching the city together in a new way.

Within the first 15 days, around 53,570 passengers used the Esplanade–Howrah Maidan stretch daily — equivalent to removing hundreds of bus trips from city roads. Many commuters switched from cabs and cars to the metro for speed, comfort, and reliability. On the very first public day, over 70,000 passengers rode the under-river section.

The underwater journey itself takes just 45 seconds. Where the bus ride across Howrah Bridge used to take 3-4 minutes on a lucky day against 15-20 minutes in heat and congestion during rush hours and sometimes up to an hour or more during political rallies and protests, commuters now travel in air-conditioned comfort. The journey from Howrah Maidan to Esplanade takes barely eight minutes by the metro. This would take a minimum of 30-40 minutes by bus.

Metro that changes daily life

For thousands in Kolkata and Howrah, the Green Line has become part of everyday life.

Shorter commutes: Travelling between Kolkata and Howrah now takes minutes instead of hours.



Comfort and reliability: Unlike road transport, the metro provides air-conditioned comfort and predictable travel times, easing stress during peak hours.

Beyond convenience, the East–West Metro addresses broader urban challenges. It reduces traffic congestion, lowers air pollution, and offers a more sustainable commute. “Howrah and Kolkata have always been twin cities, but crossing the Hooghly was a pain. The East–West Metro has changed that — Howrah now truly feels like a twin city,” said Ruby Saha, a Howrah resident.

Suburban commuters also benefit. Local train passengers arriving at Howrah Station can now interchange directly to the Green Line, avoiding crowded bus stands and congested roads.



Crowding concerns on older lines

The success of the East–West Metro has increased pressure on the North–South Blue Line, operational since 1984. Daily trains now carry more passengers, especially during evening peaks, sometimes causing overcrowding. Commuters report longer waits to board, particularly after the Green Line section opened.

While the Esplanade–Howrah Maidan stretch is fully operational, work continues to complete the 16.6-kilometre corridor from Sector V to Howrah. About 65% of the line runs through underground twin tunnels, including the 520-metre river crossing, with the rest mostly on elevated viaducts. This under-river tunnel is India’s first transportation tunnel beneath a river.

A system built for interchange

The Green Line intersects the Blue Line at Esplanade, allowing passengers to travel north to Dakshineswar or south to New Garia. Blue lights along the tunnel mark the under-river stretch, making the journey visually interesting for commuters between Howrah and Mahakaran stations.

Transforming the city’s geography

The East–West Metro has reshaped Kolkata’s daily map. By connecting previously separated neighbourhoods beneath the Hooghly, it links residential areas with IT hubs, business districts, and railway stations. Dependence on surface transport has reduced, carbon emissions have dropped, and travel is more predictable. For many, commuting has become faster, more comfortable, and less stressful.

Today, the underwater metro is not just transport — it is a living part of Kolkata’s rhythm, redefining how hundreds of thousands begin and end their daily journeys.

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