3 tunnels, 28km underground: inside India’s 306km Chennai-Bengaluru bullet train

Engineering details of India’s third bullet train corridor, linking Chennai and Bengaluru, have come into sharper focus after the Centre floated tenders for pre-construction activity on the 306.2km route. The tender directs the contractor to firm up an updated alignment for a corridor that currently spans eight stations, three of them in Tamil Nadu: Chennai Central, Poonamalle and Parandur.

The most striking engineering feature is the tunnel network. Three tunnels are planned along the corridor — a 1.7km tunnel near Chennai Central, an 11.8km tunnel cutting through the Kaundinya wildlife sanctuary in Andhra Pradesh’s mountain ranges, and a 14.7km tunnel running beneath Bengaluru’s urban core. Together, these underground stretches account for about 28km of the full 306km route.

Above ground, the corridor is designed to run elevated through Perambur, Kolathur, ICF, Madhavaram, Padi and the Chennai Bypass, before continuing along the Chennai-Thiruvallur Highway, Annanur, Poonamalle and Arakkonam. From there it tracks the upcoming Chennai-Bengaluru Expressway through Chittoor, Kolar, Kodihalli and White Field, finally terminating at Baiyappanahalli in Bengaluru.

Station planning has also shifted. The National High Speed Rail Corporation Limited had proposed a full station at Parandur in its original detailed project report, but the latest tender lists it only as a ‘future station’, with the remaining stations designated ‘stop stations’. The first station on the line will come up on the western side of Chennai Suburban Railway Station, linked to Chennai Central and its metro station via 100-metre and 50-metre connections, while the Poonamalle station will connect to the Outer Ring Road and a metro station.

Once complete, the bullet train is expected to run at 350kmph, reducing the Chennai-Bengaluru journey to under an hour, compared with roughly seven hours currently by road. Land acquisition for the project is already under way across 41 villages along the alignment, officials said.

The corridor is expected to be completed by 2035 at an estimated cost of close to ₹18,000 crore, with the final figure to be determined once the contractor submits its revised alignment study. The tender also requires the Indian Railways to coordinate with the National Highways Authority of India for connectivity with the Chennai-Bengaluru Expressway. It joins the Mumbai-Ahmedabad and Delhi-Varanasi corridors as the third bullet train project under construction in the country.

Image credit: Ministry of Railways / GODL-India.