The longest tunnel on the Lhasa-Shigatse Expressway was bored through on Sunday, marking major progress in the construction of the expressway. Located in Rinbung County in the city of Shigatse, and with an average altitude of 3,760 meters, the 4.6-kilometer-long Padangshan Tunnel is a difficult and crucial project for the second phase of the expressway, which will link the regional capital of Lhasa with Shigatse Airport. During the construction process, the builders had to overcome rock fragmentation, intense heat and other difficulties.