The Hsuehshan Tunnel is the longest tunnel in Taiwan, located on the Taipei-Yilan Freeway (Taiwan National Highway No. 5). It opened on June 16, 2006. The tunnel is bored through the Hsuehshan Range. The road connects the city of Taipei to the northeastern county of Yilan (Ilan), cutting down the journey time from two hours to just half an hour. It bypasses the rural district of Pinglin, which used to receive high traffic prior to the completion of the tunnel. One of the key aims of constructing the tunnel was to connect the western coast of Taiwan, where 95% of the population lives, to the eastern coast of the island and in doing so tackle the unbalanced development on the island. It is constructed with one pilot tunnel and two main tunnels for eastbound and westbound traffic. The total length is 12.942 km (8.042 mi), making the Hsuehshan Tunnel the second longest road tunnel in East Asia and the fifth longest road tunnel in the world. The tunnel opened in June 2006 to severe traffic jams.
Tunnel construction began in July 1991 and took 15 years to complete and cost a total of NT$90.6 billion (US$2.83 billion) to complete. Tunnel construction used 370,000 m3 (13,000,000 cu ft) of concrete, 2,000 kilometres (1,200 mi) of cables, and 2,000 lighting units.
While excavating the tunnel, engineers encountered difficult geological problems like fractured rock and massive inflows of water, which caused severe delays. One of the three TBMs on the westbound tunnel was buried by a ground collapse. In order to speed up the tunnel boring, an additional working interface in Interchange Station No. 2 (under Ventilation Shaft No. 2) was built. Along the tunnel alignment, there are six major faults, ninety-eight fracture zones, and thirty six high-pressure groundwater. Hence, serious tunnel collapses with groundwater flooding took place periodically during tunnel construction. Altogether, 25 lives were lost during 15 years of construction.
