G317, also known as northern line of Sichuan-Tibet Highway, is 2,030km long from Chengdu, Sichuan to Nagqu, Tibet, and is an important channel connecting Sichuan Province with Tibet Autonomous Region. Queershan section passes through a Puerto at 5,050m above sea level, which is the highest section of G317. With frequent traffic accidents and extremely high safety risks caused by steep terrain, severe climate and complex geological conditions, this section is called "The highest and the most dangerous section of Sichuan-Tibet Highway". The Queershan Tunnel on National Road 317 was a key construction project in China, it extends from location of the sandaoban of G317 to location of the liudaoban. It’s 12.997km long, including 7,079m tunnel length and 7,108m parallel pilot length. Tunnel entrance is at 4,378m above sea level, and the exit at 4,232m. Overall cost of the project was RMB1.116 billion including civil works cost of RMB 0.94 billion. The tunnel was constructed for 5 years, from September 2012 to September 2017 (open to traffic).