Travelers will be able to reach the Roof of the World by train within six years, thanks to technological breakthroughs by scientists and railway builders stymied for the last 50 years by frozen ground and the lack of oxygen at such a high altitude.

The 1,118-kilometre railway will extend from Lhasa, capital of Southwest China's Tibet Autonomous Region, to Golmud in neighbouring Qinghai Province.

More than 960 kilometres, or more than four-fifths of the railway will be built at an altitude above 4,000 metres. And more than half of the rails will be laid on long-frozen earth.

Workers have built bridges over areas where the earth is unstable to guarantee the Qinghai-Tibet Railway bed's safety and have constructed ventilation dykes to preserve other parts of the frozen ground.

A research report by scholars at the Xibei Science Research Institute under the China Railway Engineering Corporation said thermosiphons will make it easier to build on frozen ground.

The scholars said that thermosiphons work because they transmit heat from under the ground to the surface, not from the surface to below the ground.

This helps preserve the frozen earth, they said.

Chinese scientists started researching the challenges of tapping frozen ground in the early 1960s.

New technologies and techniques are being experimented within five frozen earth areas along the railroad.

More significant breakthroughs have been made in terms of oxygen and water shortages.

The lack of oxygen at such high altitudes has not caused any deaths among workers who began the project last year, officials said.

( China Daily July 16, 2002)