As part of the primary north-south route between Kabul, Afghanistan, and Central Asia, the Salang Tunnel provides critical passage through the Hindu Kush Mountains. Built in the 1960s, the 2.6-kilometer tunnel is in dire need of repair to fix its leaking roof, uneven surface, and failing lighting and ventilation systems. These problems pose extreme danger to travelers, and cause backups that can last more than two weeks at a time. Recognizing the importance of the tunnel for economic growth in Afghanistan, the U.S. Agency for International Development (USAID) turned to Tetra Tech to assess the most viable options for the roadway corridor.

USAID selected Tetra Tech to conduct a feasibility study that involved engineering and economic evaluations of existing conditions, development of traffic, operation and maintenance (O&M) forecasts, and recommendations for capital investment alternatives for providing north-south travel capacity.

Tetra Tech considered a number of options, which roughly fell into three groups: improvements along the existing corridor; construction of a new corridor; or construction of bypass routes to the east or west. Options were further evaluated to estimate their overall duration (design plus construction), capital cost (design and construction), O&M costs, environmental concerns, and economic impacts.

Tetra Tech ranked the most favourable options as (1) construction of a new two-lane tunnel for northbound traffic located approximately 200 meters east of and parallel to the existing tunnel and (2) the rehabilitation of the existing tunnel and two-lane roadway surface from Jabal Seraj to Khinjan for two-lane southbound traffic. This package improves the level of service of the corridor, and puts the transportation system in place to help meet Afghanistan’s long-term economic development goals.