World’s Longest Highway Tunnel : Atal Tunnel

World’s Longest Highway Tunnel – Atal Tunnel

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The Atal Tunnel, also known as the Rohtang Tunnel, is a highway tunnel constructed under the Rohtang Pass in the eastern Pir Panjal range of the Himalayas on the National Highway 3 in Himachal Pradesh, India. Named after former Prime Minister of India, Atal Bihari Vajpayee, it holds the record for being the highest highway single-tube tunnel above 10,000 feet (3,048 m) in the world.

Key Features of the Atal Tunnel

Length9.02 km (5.6 mi)
Shape (cross-section)Horseshoe
Finished width10.00 m (32.8 ft) at road level (8m pavement and 1m footpath on both sides)
Geology of tunnelling mediaUniformly dipping alternate sequence of quartzites, quartzitic schists, and quartz-diorite-schist with thin bands
General altitude3,000–3,100 m or 9,840–10,170 ft
Construction techniqueDrill and blast with NATM
Support systemFibre-reinforced concrete (100–300mm or 0–10 inch thick) combined with rock bolt (26.50mm dia, 5,000–9,000mm or 200–350 inch long)
Tunnel ventilationSemi-transverse system of ventilation
Emergency tunnelA 2.25 m high and 3.6 m wide emergency tunnel is integrated into the tunnel cross-section beneath the main carriageway
Project CostApproximately ₹3,200 crore

Impact on Travel

The Atal Tunnel significantly reduces the travel time and overall distance between Manali and Keylong on the way to Leh. The route, which previously went through Gramphu, was 116 km (72.1 mi) long and took 5 to 6 hours in good conditions. With the new route via the tunnel, the total distance travelled is brought down to 71 km (44.1 mi) which can be covered in about 2 hours, a reduction of around 3 to 4 hours when compared to the earlier route.

Atal Tunnel: Distance between Manali and Keylong on the way to Leh

Comparison with Other Tunnels

The 9.02 km (5.6 mi) long Atal Tunnel is presently the world’s longest single-tube highway tunnel at an altitude above 3,000 m(10,000 ft). There are some railway tunnels like the 32.645 km long New Guaijiao Railroad Tunnel at 3,300 meters above sea level in China. Higher but shorter tunnels in China include the 7.1-kilometre Que’ershan Tunnel at 4378 meters and the 5.7-kilometre Milashan Tunnel at 4774 meters.

Challenges Faced During Construction

The most challenging task was to continue the excavation during heavy snowfall in winter. Excavation for tunnelling was done from both ends. However, as Rohtang Pass closes during the winter, the north portal was not accessible during winter and the excavation was being done only from the south portal in winter.


The Atal Tunnel is a testament to human ingenuity and perseverance. Despite the numerous challenges faced during its construction, it stands today as a marvel of engineering and a boon for travelers and commuters alike.

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Frequently Asked Questions

How long is the Atal Tunnel?

– The Atal Tunnel spans a length of 9.02 kilometers, making it the longest highway single-tube tunnel above 10,000 feet in the world.

Elevation: It sits at an elevation of 3,100 meters (10,171 feet), while the Rohtang Pass is at 3,978 meters (13,051 feet).

Why was the Atal Tunnel constructed?

Year-round Connectivity: The tunnel ensures year-round connectivity to Ladakh, linking it to Manali and Chandigarh without relying on the snow-covered Rohtang Pass in winter.

Strategic Advantage: It benefits the armed forces by providing uninterrupted troop and supply movements to border areas.

What safety features does the Atal Tunnel have?

The tunnel is equipped with:
Semi-transverse ventilation
SCADA-controlled firefighting systems
Monitoring systems for lighting
Emergency telephone connections every 150 meters
Fire hydrants every 60 meters
CCTV cameras every 250 meters
Emergency exits every 500 meters

How has the Atal Tunnel impacted the region?

Boost to Tourism: The tunnel improves livelihoods for residents in Lahaul Valley and Ladakh, enhancing tourism prospects.

Farmers and Markets: Easier access to Delhi and other markets benefits farmers, ensuring crops like peas and potatoes reach markets without spoiling.

Overall Connectivity: It significantly shortens travel time between Manali and Leh, benefiting both locals and tourists.

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