Second TBM Arjuna Signals Accelerated Tunnelling Progress

Tunnelling work has commenced for the 11.84-km Thane–Borivali Twin Tunnel, set to be India's longest urban road tunnel, marking a key milestone in Mumbai's infrastructure development. TBM 'Arjuna' site acceptance test (SAT) was completed on 25 June 2026 and is now ready for initial drive. This follows TBM 'Nayak' site acceptance test completion on 26 February 2026 and its launch on 7 April 2026.

The 11.84 km corridor will cut travel time from 60–90 minutes to 15 minutes, easing congestion and boosting connectivity across the region. As of 31 August 2025, the project achieved over 8 per cent physical progress, with steady advancement expected following the TBM launch. Physical progress of the project reached 13.13% as of July 2026.

The 13.34-meter Single Shield TBM is India's largest diameter ever for any urban project, and the first of its kind in metro cities. The deployment includes four advanced TBMs, including one of India's largest single-shield hardrock TBMs. Once completed, these 3-lane twin tunnels, measuring 5.75 km and 6.09 km respectively, will be India's longest underground road tunnels, specifically designed for traffic management in a metro city.

The project's environmental engineering is equally ambitious. The alignment passes beneath the Sanjay Gandhi National Park and is being executed using advanced TBM technology to minimise ground disturbance. The project will adopt safety protocols inspired by international benchmarks, including those used in Singapore's metro systems, which tunnel through water-bearing strata. The TBM is equipped with automated debris removal systems, emergency response modules, and enhanced worker protection features.

Each tunnel will feature three lanes, including a dedicated emergency lane, with cross-passages every 300 metres. Upon completion, the Thane–Borivali Twin Tunnel is expected to ease congestion on Ghodbunder Road, which currently carries approximately 1 to 1.2 lakh passenger car units daily.

The Thane–Borivali Twin Tunnel Project is a flagship project of the MMRDA aimed at significantly enhancing east–west connectivity across the Mumbai Metropolitan Region. By reducing vehicle idling and long detours, the tunnel is projected to cut CO2 emissions by up to 36 percent, with fuel savings estimated at around 10.5 lakh metric tonnes annually. Infrastructure experts view this as transformative for real estate markets along the corridor, particularly in Thane and Borivali, where improved connectivity is expected to drive residential and commercial development.