Cho La Mountain Tunnel

Cho La Mountain Tunnel

Located in the Cho La Mountains, in western Sichuan Province, China, the Cho La Mountain Tunnel is said to be one of the world’s highest vehicular tunnels at an average altitude of 4.378m (14,363ft) above the sea level.

The tunnel, also known as Que'ershan Tunnel, bores through the Cho La mountains at an altitude of 4.232m to 4.378m above the sea level. Its surface is asphalt. The tunnel opened to traffic on Sept 26, 2017, 15 years after the project was started, above the Que'ershan Mountain, in the Shaluli Mountains range, that stands 6,168 meters above the sea level. Its length, the thin air and low temperatures at that altitude all contributed to the complexity of the construction. The two-way tunnel has a speed limit of 40 kph and takes around 10 minutes to pass through.
The tunnel, which cuts through Cho La Mountain on the Qinghai-Tibet Plateau, is 7km long with more than 5 km of auxiliary roads. Built at a cost of 1.15 billion yuan (170 million U.S. dollars), it is part of the National Highway G317 that connects the city of Chengdu to the Tibetan town of Nagqu.
Before the tunnel was opened this week, drivers had to negotiate a treacherous mountain route prone to landslides, avalanches, rockfalls, blizzards and ice, climbing up the Chola Shan Pass, a mountain pass at 4.920m (16,141ft) above the sea level. The tunnel greatly shortens the travel time (by 2 hours), and avoids the most dangerous section on the route. Previously vehicles spent more than two hours driving around the mountain on a road threatened by landslides, blizzards and slippery ice. 
Pic: http://german.cri.cn/3105/2017/11/15/1s271643.htm