Longest Bridges, Tunnels and Highways

Transport infrastructure serves as the backbone of economic integration, tactical defense, and spatial connectivity. For UPSC Civil Services aspirants, a precise breakdown of the longest bridges, tunnels, and highways—both globally and within India—offers critical insights into physical geography, regional planning, and advanced structural engineering.

Global and National Bridging Infrastructure: Engineering over Water and Terrain

Bridges are structurally classified based on their load-bearing mechanisms into beam, cantilever, arch, suspension, and cable-stayed systems. Their development is dictated by hydrological dynamics, geological stability, and transit capacity.

The World’s Longest Bridges

Danyang–Kunshan Grand Bridge (China)

The Danyang–Kunshan Grand Bridge holds the definitive record as the world’s longest bridge, spanning 164.8 kilometers along the Beijing–Shanghai High-Speed Railway.

• Geomorphological Setting: It traverses the alluvial plain of the Yangtze River Delta, characterized by low-lying rice paddies, canals, lakes, and swampland.
• Structural Design: Engineered as a continuous viaduct, it sits on approximately 9,500 concrete pillars. It includes a 9-kilometer section that spans open water across Yangcheng Lake in Suzhou.

Changhua–Kaohsiung Viaduct (Taiwan)

Covering a total distance of 157.3 kilometers, this viaduct acts as a key structural segment for the Taiwan High-Speed Rail network.

• Seismic Design: It is built as a series of connected viaducts engineered to handle seismic activity. This design allows the transit line to survive earthquakes and fault ruptures common along the active plate boundary of Taiwan without structural failure.

Cangde Grand Bridge (China)

Ranking as the third-longest bridge globally, this high-speed rail viaduct runs for 115.9 kilometers along the Beijing–Shanghai transit corridor. Its structural design utilizes reinforced concrete box girders engineered to withstand high lateral seismic forces.

India’s Longest Bridges

Atal Setu (Mumbai Trans Harbour Link – MTHL)

The Atal Bihari Vajpayee Sewri–Nhava Sheva Atal Setu is India’s longest bridge and longest sea bridge, spanning a total length of 21.8 kilometers.

• Geographic Alignment: It connects Sewri in South Mumbai to Chirle in Navi Mumbai across the Thane Creek, cutting transit time down from 2 hours to 20 minutes.
• Engineering Innovations: The marine section covers 16.5 kilometers, while the overland approaches span 5.3 kilometers. It is India’s first project to use Orthotropic Steel Decks (OSDs), which allow for longer spans with fewer pillars to preserve marine transit lanes.

Dhola–Sadiya Bridge (Bhupen Hazarika Setu)

Measuring 9.15 kilometers in length, this is India’s longest river bridge spanning open water.

• Geographic Placement: It crosses the Lohit River, a major tributary of the Brahmaputra, connecting Assam and Arunachal Pradesh.
• Strategic Utility: It is engineered to support the weight of 60-ton main battle tanks, like the T-90, ensuring rapid mobilization for the Indian Army along the Line of Actual Control (LAC).

Dibang River Bridge

Spanning 6.2 kilometers across the Dibang River in Arunachal Pradesh, this structure forms a critical link along the Trans-Arunachal Highway, ensuring year-round connectivity to the eastern border outposts.

Mahatma Gandhi Setu

Extending 5.75 kilometers over the Ganga River, this river bridge connects Patna in the south to Hajipur in north Bihar. It was recently retrofitted from a distressed concrete cantilever system into a modern steel truss design.

Global and National Tunnelling Infrastructure: Subterranean and Alpine Engineering

Tunnels are engineered to bypass high-altitude topography, marine choke points, or urban density. They require advanced geotechnical excavation techniques, such as the New Austrian Tunnelling Method (NATM) and Tunnel Boring Machines (TBMs).

The World’s Longest Tunnels

Gotthard Base Tunnel (Switzerland)

The Gotthard Base Tunnel is the longest and deepest rail tunnel globally, extending 57.1 kilometers through the Swiss Alps.

• Geological Challenges: It runs up to 2,450 meters below the mountain surface, requiring engineers to manage extreme rock pressure and temperatures that reach 46 degrees Celsius inside the excavation zone.
• Strategic Importance: It bypasses the high-altitude Alps, shifting freight transit from road to rail along Europe’s main economic corridor.

Seikan Tunnel (Japan)

Spanning 53.85 kilometers, the Seikan Tunnel connects the islands of Honshu and Hokkaido beneath the Tsugaru Strait.

• Undersea Profile: A 23.3-kilometer section of the tunnel sits 100 meters below the seabed, excavated through unstable volcanic rock layers that required continuous chemical grouting to stop seawater seepage.

Channel Tunnel (Eurotunnel)

Connecting Folkestone, United Kingdom, with Coquelles, France, this rail tunnel measures 50.45 kilometers in length. It features the longest continuous undersea segment of any tunnel globally, stretching 37.9 kilometers beneath the English Channel.

India’s Longest Tunnels

Atal Tunnel (Rohtang)

The Atal Tunnel is the world’s longest highway tunnel above an altitude of 10,000 feet (3,048 meters), measuring 9.02 kilometers.

• Geographical Alignment: Cut through the Pir Panjal range of the Himalayas beneath the Rohtang Pass, it ensures year-round connectivity between Manali and the Lahaul-Spiti valley, bypassing a route previously blocked by heavy snow for six months.
• Strategic Value: It serves as a vital logistics route for supplying military personnel deployed in the Ladakh sector.

Syama Prasad Mookerjee Tunnel (Chenani-Nashri)

Spanning 9.28 kilometers along National Highway 44 (NH 44) in Jammu and Kashmir, this is India’s longest bidirectional highway tunnel. It bypasses snow-prone stretches of the outer Himalayas, lowering the transit elevation by 340 meters.

Pir Panjal Railway Tunnel (T-80)

Extending 11.21 kilometers through the Pir Panjal Range, this is India’s longest operational rail tunnel. It forms a core component of the Jammu–Udhampur–Srinagar–Baramulla Rail Link (USBRL) project.

T-50 Rail Tunnel

The T-50 tunnel, located on the Khari-Sumber section of the USBRL project, spans 12.75 kilometers, making it the longest transportation rail tunnel in India.

Global and National Expressways and Highways: Arterial Networks

Highways and expressways facilitate cross-continental trade and inter-state logistics. They are engineered for high-velocity transit, managed access, and heavy axle loads.

The World’s Longest Highways

Pan-American Highway

Spanning approximately 30,000 kilometers, the Pan-American Highway is the longest integrated vehicular road network globally.

• Geographic Scope: It stretches across the Americas from Prudhoe Bay, Alaska, to Ushuaia, Argentina.
• The Darién Gap Exception: The continuous highway network is interrupted by a 106-kilometer break known as the Darién Gap. This region consists of dense, undeveloped rainforest, swathes of swampland, and indigenous protected zones between Panama and Colombia where road construction is restricted.

Highway 1 (Australia)

Measuring 14,500 kilometers, Highway 1 is the longest national highway that runs as a single, continuous route within a single sovereign nation. It completely rings the Australian continent, linking all major mainland state capitals.

Trans-Siberian Highway

Spanning roughly 11,000 kilometers across Russia, this highway runs from St. Petersburg on the Baltic Sea to Vladivostok on the Pacific Ocean, serving as the main domestic land bridge across Eurasia.

India’s National Highway Framework

The Ministry of Road Transport and Highways (MoRTH) manages India’s primary road transport network. National Highways are numbered systematically based on a geographical grid: North-South highways carry even numbers that increase from east to west, while East-West highways carry odd numbers that increase from north to south.

National Highway 44 (NH 44)

NH 44 is India’s longest continuous National Highway, spanning 4,112 kilometers.

• Route Configuration: It originates in Srinagar (Jammu and Kashmir) and terminates at Kanyakumari (Tamil Nadu).
• States Traversed: It passes through 11 states and union territories, merging seven older national highway designations (including NH 1A, NH 1, NH 2, and NH 7).

National Highway 27 (NH 27)

NH 27 is India’s second-longest national highway, covering 3,507 kilometers. It serves as the main east-west arterial axis of the Golden Quadrilateral’s East-West Corridor, running from Porbandar in Gujarat to Silchar in Assam.

The Golden Quadrilateral Network

This 5,846-kilometer national highway network connects India’s four major urban economic hubs: Delhi (North), Mumbai (West), Chennai (South), and Kolkata (East).

Statistical Summary Matrix of Infrastructure Extremes

Key Structural and Strategic Concepts for Civil Services Evaluation

Orthotropic Steel Decks (OSDs)

OSDs are specialized structural components consisting of flat steel plates stiffened by longitudinal ribs. This setup creates a lightweight deck that distributes vehicle loads evenly, allowing for longer spans between bridge piers. This technology was heavily utilized in India’s Atal Setu to reduce the structural footprint in Thane Creek’s eco-sensitive marine zone.

New Austrian Tunnelling Method (NATM)

NATM is an observational tunneling method where the surrounding rock mass acts as a primary support mechanism. Real-time geological monitoring guides the continuous application of shotcrete (sprayed concrete) and rock bolts directly after excavation, adapting to the shifting pressure of the rock.

Tunnel Boring Machines (TBMs)

TBMs, also known as “mechanical moles,” are massive cylindrical machines used to excavate tunnels through rock and soil layers. They cleanly cut through geological strata while simultaneously installing precast concrete tunnel segments, minimizing disruption to surface structures and ecosystems above.

The Darién Gap

The Darién Gap is a 106-kilometer break in the Pan-American Highway located on the border between Panama and Colombia. It remains unpaved due to a combination of dense rainforest geography, steep terrain, and active environmental preservation efforts designed to prevent the spread of agricultural diseases between continents.