The Mila Mount Tunnel on the Lhasa-Nyingchi Highway in China's Tibet autonomous region began operations on Friday, symbolizing the full operation of another vital traffic line in the region.

The tunnel is located at the junction of Lhasa and Nyingchi at an average altitude of 4,750 meters above sea level, according to the China Railway Erju Construction Co., Ltd, which constructed the project.

As a key section of the Lhasa-Nyingchi Highway on the National Highway 318, the left lane of the tunnel is 5,727 meters and the right lane is 5,720 meters long respectively, according to the company.

Construction of the Mila Mount tunnel started in April 2015, and it has become the world's highest super-long tunnel, the company said.

Linking the regional capital city Lhasa with the region's eastern tourism city of Nyingchi, the 409-kilometer highway has reduced travel time from the previous eight hours to the current four.