Work is underway on China's second railway line to Tibet that will wind through some of the world's most mountainous and inhospitable territory and likely take the better part of a decade to complete, state media said Wednesday.
Work at the line's two ends in Chengdu, the capital of Sichuan province, and Tibet's capital of Lhasa has already begun, the official Xinhua News Agency reported.
Other feasibility studies have been completed, but the most difficult section, through the mountains from Kangding in Sichuan to Nyingchi in Tibet, is still being designed and may take seven years to finish once construction begins, Xinhua said.
Once completed, the line will run for 1,700 kilometers (1,060 miles), 80 percent of it consisting of tunnels and bridges. Total cost is estimated at 250 billion yuan ($37 billion), while the travel time from Chengdu to Lhasa will be cut from 48 to about 13 hours, Xinhua said.
Likening it to a roller coaster, designers said the line will traverse eight ascents and descents, topping out at 4,400 meters (14,400 feet), Xinhua said. Varying terrain, landslides and earthquakes are also major threats.
"It will be the most difficult super project in railway construction history," Xia Lie, a senior engineer at China Railway Eryuan Engineering Group, was quoted as saying.
The line is the latest in a seemingly endless series of hugely ambitious construction projects that include the gargantuan Three Gorges Dam, the world's longest bridge over water in Jiaozhou Bay and the world's most extensive high-speed rail network.
China opened an initial line to Lhasa from Qinghai province to the northeast in 2006 that runs for 1,956 kilometers (1,215 miles) and tops out at about 4,000 meters (13,000 feet).