New Guanjiao Tunnel
New Guanjiao Tunnel () is a tunnel on the 2nd line of Qinghai–Tibet Railway in Guanjiao Mountain, Qinghai province. It is dual-bored, double-track rail tunnel. The total length of the tunnel is , which makes it the longest railway tunnel in China. China Railway First Survey and Design Institute is responsible for the design. The New Guanjiao Tunnel was designed for two parallel single-track tunnels with speeds of up to . The total construction duration was projected to be 5 years. The tunnel was bored in difficult geological conditions and high altitude, exceeding  above sea level. The construction started in 2007 and was completed in April 2014. The tunnel was opened on 28 December 2014. The tunnel's northeastern portal () is in Tianjun County, the southwestern portal () is in Ulan County. References 

Railway tunnels in China
Rail transport in Qinghai