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A light at the end of the tunnel


Atal Tunnel



The need for a road through the perilous Rohtang Pass, located at an altitude of over 13,000 ft in the Pir Panjal Range of the Himalayas, was discussed as early as 1860 by the Moravian Mission.

Nearly 160 years later, the Atal Tunnel (formerly called the Rohtang Tunnel) has become a reality. After nearly a decade under construction, and despite challenges including heavy snowfall, avalanches and severe geographic conditions, the 9 km tunnel is now the world’s longest highway tunnel above an altitude of 10,000 ft.

Our role

SMEC was engaged by India’s Border Roads Organisation and the Ministry of Defence in 2006 to provide design, engineering and advisory services on the project. We then took on a subsequent role as the Independent Engineer, contributing our global expertise to helping our client make this huge undertaking a reality.    

Challenges on a once-in-a-lifetime project

The remoteness, accessibility and extreme altitude of the project presented enormous challenges to geological works, tunnelling and mechanical and electrical installations. 

The Himalayas are a thrilling but daunting environment when it comes to geological setup and challenges to large civil works. One of the most challenging sections was the Seri Nallah Fault zone, located about 1.5 km into the mountain from the south tunnel portal. Tunnelling through this crushed material with a huge material outflow was extremely challenging and took almost five years of tenacity and technical skill to complete.

Another very complex piece of work was designing a tunnel ventilation system in accordance with international best practice, considering height above sea level and the different barometric pressures at different times of year. Our specialists provided innovative solutions for the design of robust mechanical and electrical engineering systems, which are essential for fire and life safety on the project.

Delivering a nation-first

Through a persistent, collaborative effort between SMEC, our client and the contractors, the Atal Tunnel was opened to the public in 2020. The tunnel facilitates two-way traffic and is designed to cater to up to 3,000 vehicles per day in any weather conditions at a maximum vehicular speed of 80 km per hour.

Previously, access over the Rohtang Pass was limited to only six to eight months out of the year, due to heavy snowfall, avalanches and landslides. What this tunnel offers – safe, year-round road travel through the Rohtang Pass – is a game changer for India.