By last May, 1.48 million passengers have ridden the train into Tibet and 1.52 million out of Tibet, said Sun, who is also an academician with China Academy of Sciences.

Though nearly half (550 km) of the railway is built on frozen earth - under-zero soil containing ice, which thaws in warm weather and causes the earth subsidence, data show the rail tracks on frozen earth subsided less than 2 cm each year.

It is "quite an achievement", because controlling the subsidence within 30 cm can already be called the world's best record, he said.

In Russia and Canada, which also have railways on frozen earth, serious subsidence has made trains run much slower than designed, at 50-70 kph.

"Our trains have run at the designed speed of up to 100 kph," Sun said.

The railway has also survived earthquakes that shook the Tangula area four times in June 2008.

In the near future, a new railway will be built from Lhasa to Xigaze, and before 2020 a railway is planned connecting Xinjiang Uygur autonomous region and Tibet.

In the long term, there will also be railways entering Tibet from Chengdu in Sichuan province and Kunming in Yunnan province, he said.

In 2007, Tibet autonomous region gained 4.8 billion yuan from tourism revenue, up 73.3 percent year on year. Qinghai province gained 4.7 billion yuan, up 31.6 percent, according to official statistics.

-- (China Daily, Jan 11, 2009)