Changlashan tunnel, the world's highest highway tunnel, was put in service on June 25, 2015 after more than three years' endeavors by China Railway 14th Bureau Group.

Located in Zaduo county, northwest China's Qinghai province, Changlashan tunnel is 2,400 meters long, with an elevation of 4,500 meters. It is a crucial project of No. 309 highway, which is an important recovery and reconstruction project after Yushu earthquake in Qinghai province.

Gao Guangyou, a project manager of China Railway 14 Bureau Group, indicates that their workers have overcame a number of technical problems and severe altitude sickness to complete this project.