The first two-tier underpass complex for vehicles and pedestrians in the city is almost complete near the Kolkata Gate in New Town.
The upper level of the subway complex on the Major Arterial Road will be for cars and two-wheelers plying between Salt Lake and New Town, said a senior official of Hidco, which commissioned the project.
The lower tier, which was unveiled in 2021, is a fourway pedestrian subway complex located 8m below the underpass for vehicles.
Trucks, buses and heavy vehicles will travel on the surface as they do now, the Hidco official said.
“Movement of vehicles will be smoother once the volume is split,” the official said.
“Only cars and two-wheelers will be allowed to move through the underpass. Once the underpass in functional, traffic load will ease considerably at the crossing, one of the busiest in New Town where airport-bound as well as Salt Lake-bound traffic merges,” the official said.
The underpass for vehicles, built around 4.2m below the road surface, is around 320m-long and has four lanes. It spans 7m in width and has a small median divider.
A site engineer said the underpass rests on a 650mm bed slab of reinforced concrete cement (RCC), which in turn rests on a bed of sand that os 1m deep. A layer of pavement-quality concrete reinforces the foundation.
“Our main challenge was to ensure that the existing underpass network (for pedestrians) did not get damaged. All our measurements had to be absolutely perfect and there was no room for error,” said the engineer.
On Friday, this newspaper spotted workers painting the interiors of the underpass. Once the paint job is over, a layer of concrete will be laid.
Officials said a flyover could not have been constructed at the intersection because of the Kolkata Gate.
A survey was conducted and experts said that an underground tunnel was the only solution to the traffic congestion on the stretch.
The Major Arterial Road is one of the arteries that connect the airport with the rest of the city.
The road also leads to Sector V and Salt Lake from New Town and witnesses a high volume of traffic during rush hours.