The Qinghai-Tibet Railway, the world's highest plateau railway, has stood safety and environmental tests while boosting regional economic growth over the past five years.

Friday marks five years since the railway opened.

The 1,956-km rail link running from Golmud in the northwestern Qinghai Province to Tibet's regional capital Lhasa has transported more than 41 million passengers and 180 million tonnes of cargo since it opened on July 1, 2006, sources with the railway operator said Thursday.

Last year, the railway carried 9.7 million passengers and 48 million tonnes of goods, compared with 6.4 million people and 24 million tonnes of goods in 2006, said Miao Xiaohua, deputy manager of Qinghai-Tibet Railway Company.

Tibet Autonomous Region received 6.8 million tourists in 2010, 3.8 times the 2005 figure, said Wang Songping, Tibet's deputy tourism official.

"Last year, 42 percent of the tourists traveled by train, a sharp rise from 26 percent reported in 2006," Wang said.

By the end of 2015, Tibet expects to host 15 million tourists annually and post an annual tourism revenue of 18 billion yuan (2.8 billion U.S. dollars), he said.

ADDRESSING ENVIRONMENTAL CONCERNS

The Qinghai-Tibet Railway passes through three national nature reserves including Hoh Xil, a major habitat for the critically-endangered Tibetan antelope.

Perched at an average altitude of 4,500 meters, Hoh Xil reserve contains the largest area of uninhabited land in China and is dubbed the country's "last haven for wild animals."

Pregnant antelope cows, often followed by young members of the herd, migrate to Hoh Xil every June to give birth, and leave the reserve in September.

"The number of antelopes that make the migration has apparently risen in recent years," said Xiao Penghu, deputy chief of Hoh Xil Nature Reserve Administration.

Xiao said some people had thought the roaring trains might scare away the antelopes and disrupt their breeding pattern, but in fact their population in the Hoh Xil region had increased from around 50,000 in 2006 to more than 60,000 currently.

Thirty-three special passageways were built along the Qinghai-Tibet Railway enabling animals to follow their normal migration routes unhindered.

"I see herds of Tibetan antelopes going through these passageways every summer," said truck driver Li Jingui who drives along the route every year.

The Qinghai-Tibet Plateau used to have millions of Tibetan antelopes, but hunting and destruction of their habitat had decimated the population over the past decades.

Poachers hunt the antelopes for their hides as it can be sold and made into shahtoosh shawls, a luxury item that requires three to five antelope skins to make just one shawl.

Since 1979, the animal has been recognized as an endangered species and protected under the Convention on the International Trade in Endangered Species.

"We've been watching out for potential pollution all these years," said Wang Zhiwei, a maintenance engineer with Qinghai-Tibet Railway Company.

Wang and his colleagues monitor all the 15 sewage treatment stations along the Golmud-Lhasa section of the railway every month to ensure sewage is treated properly and causes no pollution to the plateau air and water.

All the stations use clean energy to minimize emissions.

Meanwhile, railway authorities have worked to preserve and expand vegetation along the route, which is surrounded by 675 km, or 5.6 million square meters, of trees.