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Geography May 01, 2026 6 min read Daily brief · #12 of 35

‘World’s widest underground tunnel’—Mumbai-Pune ‘missing link’ opens with a Guinness World Record

The Mumbai-Pune Expressway 'Missing Link' project was inaugurated on 1 May 2026 — Maharashtra Day — with the opening of two new tunnels completing the previo...

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What Happened

  • The Mumbai-Pune Expressway 'Missing Link' project was inaugurated on 1 May 2026 — Maharashtra Day — with the opening of two new tunnels completing the previously fragmented expressway corridor.
  • The project's principal tunnel has been officially recognised by Guinness World Records as the world's widest underground road tunnel, with a width of 22.33 metres.
  • The Missing Link spans 13.3 km in total, of which approximately 10.67 km comprises five-lane twin tunnels, each 22.33 metres wide, built through the challenging terrain of the Sahyadri mountain range.
  • The project involved the excavation of over 85 lakh tonnes of rock, including tunnelling beneath Lonavala Lake, and construction of viaduct structures 180 metres high across valleys.
  • The project cost approximately Rs 7,000 crore and was executed by infrastructure contractors AFCONS and Navayuga through the Sahyadri mountain section.
  • The new link cuts travel time between Mumbai and Pune by approximately 30 minutes, replacing the previously dangerous and congested ghat section of the old expressway.

Static Topic Bridges

The Mumbai-Pune Expressway (officially the Yashwantrao Chavan Expressway) was India's first six-lane concrete expressway, opened in 2002, connecting India's financial capital to its eighth-largest city. However, the expressway had a critical 'missing link' — a section near the Sahyadri ghats where the expressway broke, forcing traffic onto the older and more dangerous Mumbai-Pune highway through steep ghat sections prone to accidents and congestion, particularly near Khopoli and Lonavala.

  • The Yashwantrao Chavan Expressway is operated by the Maharashtra State Road Development Corporation (MSRDC), a state agency — distinct from NHAI (National Highways Authority of India), which manages national highway projects.
  • The Missing Link project has been under planning and construction for over a decade, delayed by the engineering complexity of tunnelling through the Sahyadri ranges and environmental clearance requirements.
  • The missing link section connects Khopoli to Sinhagad, completing an uninterrupted, high-speed expressway corridor between the two cities.
  • The Sahyadri mountain range (part of the Western Ghats) poses extreme geological challenges including fractured basalt rock, underground water bodies, and proximity to the ecologically sensitive Western Ghats — a UNESCO World Heritage Site.

Connection to this news: The inauguration resolves a 24-year gap in the Mumbai-Pune Expressway's design, completing one of Maharashtra's most significant infrastructure projects and demonstrating India's growing capacity for complex underground civil engineering.

New Austrian Tunnelling Method (NATM)

The Missing Link tunnels were constructed using the New Austrian Tunnelling Method (NATM), a globally recognised construction technique that treats the rock surrounding a tunnel as an active structural component rather than merely an obstacle to be removed. NATM uses a combination of sprayed concrete (shotcrete), rock bolts, and continuous geotechnical monitoring to stabilise the tunnel as excavation progresses.

  • NATM is also known as the Sequential Excavation Method (SEM) or Sprayed Concrete Lining (SCL) method.
  • The method was developed in Austria in the 1960s by engineers Ladislaus von Rabcewicz and Leopold Muller for Alpine tunnelling conditions.
  • In India, NATM was first applied at scale in the Pir Panjal Railway Tunnel (Jammu & Kashmir) and subsequently used in the Atal Tunnel (Rohtang), USBRL (Udhampur-Srinagar-Baramulla Rail Link) tunnels, and metro rail projects.
  • NATM is preferred in India for mountain tunnels because it adapts to highly variable geological conditions — essential in the Himalayan and Western Ghats regions where rock quality can change dramatically within short distances.
  • The Sahyadri's basalt geology, combined with proximity to Lonavala Lake, required NATM's real-time monitoring to manage groundwater ingress and prevent surface settlement above the tunnel.
  • The world-record 22.33-metre width of the tunnel required an exceptionally large cross-section — a technical feat made possible through NATM's flexibility in accommodating non-standard tunnel profiles.

Connection to this news: The world's widest underground road tunnel was achievable through NATM's adaptability to the Sahyadri's challenging geology — a demonstration of India's advancing tunnelling engineering capability that has implications for future infrastructure projects in mountain corridors.

National Infrastructure Pipeline (NIP) and Infrastructure Financing

The Mumbai-Pune Missing Link is part of India's broader infrastructure push, articulated through the National Infrastructure Pipeline (NIP) — a government initiative to channel large-scale investment into transport, energy, urban, and social infrastructure.

  • The NIP was launched in 2019 with a total outlay of Rs 111 lakh crore for FY 2020–25, extended subsequently to cover post-2025 projects.
  • Road and highway infrastructure accounts for approximately 18% of NIP investment, making it the second-largest sector after energy (24%).
  • NHAI (National Highways Authority of India) and NHIDCL (National Highways and Infrastructure Development Corporation Limited) are the two primary central agencies for national highway development. NHIDCL specifically targets strategic highway projects in northeastern states and border areas.
  • The NIP is jointly funded: Central government (39%), state governments (40%), and private sector (21%) — reflecting a significant state government role, which is relevant for MSRDC-executed projects like the Missing Link.
  • Infrastructure financing mechanisms include budget allocation, PPP (Public-Private Partnership) models, National Monetisation Pipeline (NMP), and sovereign bond issuances.
  • Tunnel and mountain road projects typically have significantly higher per-km costs than flat terrain highways: the Missing Link cost approximately Rs 526 crore per km, compared to Rs 15–25 crore per km for four-lane plains highways.

Connection to this news: The Rs 7,000-crore Missing Link project exemplifies the high-cost, high-complexity end of India's infrastructure build-out — where conventional cost benchmarks do not apply and specialised financing and execution frameworks are essential.

Western Ghats and Environmental Considerations in Infrastructure Projects

The Sahyadri mountain range forms the northern section of the Western Ghats, one of the world's eight "hottest hotspots" of biological diversity and a UNESCO World Heritage Site. Infrastructure development in this ecologically sensitive zone must navigate stringent environmental clearance requirements.

  • The Western Ghats cover approximately 140,000 sq km across Gujarat, Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu; they are the source of major peninsular rivers including the Krishna, Godavari, Kaveri, and Tungabhadra.
  • The Kasturirangan Committee Report (2013) designated approximately 37% of the Western Ghats as an Ecologically Sensitive Area (ESA), imposing restrictions on mining, quarrying, and major construction.
  • Infrastructure projects within or adjacent to Western Ghats ESA require Environmental Impact Assessments (EIA), Forest Clearance under the Forest Conservation Act, 1980, and Wildlife Clearance if the project affects wildlife habitats or corridors.
  • The Missing Link tunnel goes beneath Lonavala Lake, a water body in the Sahyadri zone — requiring specialised hydrogeological studies and waterproofing engineering to prevent lake bed subsidence and groundwater contamination.
  • Tunnelling is generally preferred over open-cut highways in ecologically sensitive mountain terrain because it minimises surface disturbance, limits deforestation, and reduces landslide risk compared to road-cutting on slopes.

Connection to this news: The choice to build tunnels rather than surface roads through the Sahyadri was partly driven by ecological sensitivity to the Western Ghats — making the Missing Link project a case study in balancing infrastructure imperatives with environmental protection in a biodiversity-critical zone.

Key Facts & Data

  • Project name: Mumbai-Pune Expressway Missing Link (Yashwantrao Chavan Expressway completion)
  • Executing agency: Maharashtra State Road Development Corporation (MSRDC), contractors AFCONS and Navayuga
  • Total project length: 13.3 km (of which 10.67 km in twin tunnels)
  • Tunnel width: 22.33 metres (each tube), five lanes — Guinness World Record for world's widest underground road tunnel
  • Project cost: Approximately Rs 7,000 crore
  • Rock excavated: Over 85 lakh tonnes through Sahyadri (Western Ghats) basalt
  • Inauguration date: 1 May 2026 (Maharashtra Day)
  • Travel time saving: Approximately 30 minutes between Mumbai and Pune
  • Tunnelling method: New Austrian Tunnelling Method (NATM) / Sequential Excavation Method
  • Notable engineering challenge: Tunnelling beneath Lonavala Lake; viaducts 180 metres high across valleys
  • Western Ghats: UNESCO World Heritage Site; Kasturirangan Committee ESA designation covers 37% of the Ghats
  • NHAI manages national highways; NHIDCL covers strategic/border infrastructure; MSRDC manages Maharashtra expressways
  • National Infrastructure Pipeline: Rs 111 lakh crore outlay (FY 2020–25); roads account for 18% of investment
On this page
  1. What Happened
  2. Static Topic Bridges
  3. Mumbai-Pune Expressway: Background and the 'Missing Link' Problem
  4. New Austrian Tunnelling Method (NATM)
  5. National Infrastructure Pipeline (NIP) and Infrastructure Financing
  6. Western Ghats and Environmental Considerations in Infrastructure Projects
  7. Key Facts & Data
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