Construction of the Mumbai metropolitan region’s landmark underground road corridor is preparing to enter its next engineering phase, with a second tunnel boring machine expected to begin excavation from the Thane side in the coming days. The development is significant as it advances one of India’s largest urban transport projects aimed at improving regional connectivity while attempting to minimise environmental disruption beneath the Sanjay Gandhi National Park. Project officials indicate that excavation activity will soon accelerate after the successful deployment of the first tunnel boring machine earlier this year. The second machine will work simultaneously from the Thane portal, increasing tunnelling capacity for the Mumbai Twin Tunnel Project, while excavation from the Borivali side is expected only after pending land acquisition and rehabilitation processes are completed.
The 11.84-kilometre corridor, including more than 10 kilometres of underground twin tunnels, has been designed to establish a direct road connection between Thane and Borivali, reducing dependence on the heavily congested Ghodbunder Road. Transport planners believe the corridor could substantially improve east-west mobility across the Mumbai Metropolitan Region, where travel demand continues to outpace road capacity. According to officials, the Borivali launch site still requires the relocation of a small number of project-affected households before construction can commence from the western end. Rehabilitation measures have already been implemented for most affected families through public housing schemes, while authorities continue efforts to complete the remaining resettlement process. Urban development experts note that timely and equitable rehabilitation remains essential to ensuring that large infrastructure projects progress without creating long-term social challenges. The Mumbai Twin Tunnel Project will eventually deploy four hard-rock tunnel boring machines capable of excavating through the region’s basalt formations.
The machines incorporate automated tunnel lining systems, precision guidance technology and advanced safety features that allow excavation to proceed beneath ecologically sensitive landscapes with limited surface disturbance. Engineers say this approach reduces vibration, protects surface ecosystems and improves construction safety compared with conventional excavation methods. Once operational, the underground corridor is expected to reduce journey times between Thane and Borivali from well over an hour during peak traffic to nearly 15 minutes. The project will also integrate with other regional road infrastructure, offering improved connectivity for vehicles travelling from Nashik, Navi Mumbai and Kalyan towards Mumbai’s western suburbs. Urban mobility specialists, however, caution that faster road connectivity should be complemented by stronger public transport networks and demand management strategies to avoid generating additional private vehicle traffic over the long term. While reduced idling and smoother traffic flow may lower emissions initially, sustainable mobility outcomes will depend on integrating road infrastructure with metro, bus and non-motorised transport systems.
The project includes cross-passages for emergency evacuation, mechanical ventilation, fire safety systems, intelligent monitoring and environmental mitigation measures, including compensatory tree plantation. As tunnelling activity expands over the coming months, the pace of construction, rehabilitation efforts and ecological safeguards will remain key indicators of whether the corridor can balance infrastructure delivery with responsible urban development.
