The new line will open up travel to Tibet

These workers have left behind homes and families far away. For the next seven years this railway line will be their life.

It is all part of China's grand plan to open its vast but remote interior. Even the workers have learned the mantra of the Tibet railway.

You Kaixuan, a labourer from Gansu province, says it is a great thing for the Chinese people and will bring development and prosperity to Tibet.

China's motive

The railway will be a tremendous feat of engineering - the highest line ever built, most of it more than 4,000m above sea level. It must cross ever-shifting permafrost - all to link poor and backward Tibet to the Chinese heartland.

China says it is all about economics, about bringing greater prosperity to Tibet, but from an economic point of view this railway really makes very little sense. It is less about economics than it is about securing political control over China's restive Tibetan territories.

At the current end of the line in Golmud the central market bustles with activity. This dusty, windswept city stands at the foot of the mighty Kunlun mountains, the wall of rock and ice that for centuries has ensured Tibet's isolation.

Forty years ago, before the railway came, there was nothing here, just open steppe and wandering Tibetan herdsmen. But today Golmud is home to 200,000 people, almost all of them immigrants from eastern China. Less than 5% of the population is Tibetan.

Tibet's fears

Wandering through the market, I meet Tashi, a barrel-chested Tibetan herder with an unlikely looking cowboy hat, sparkling green eyes and a permanent grin on his sun-baked face. Tashi and his herds live in the high mountains that border Qinghai and Tibet.

He is deeply concerned about what the new railway will bring.

"The railway is bad," he says. "It may help develop the economy but it will mean a lot of people from outside will move into Tibet.

"It used to be our place, but with the railway all kinds of people will come."

According to Tibetan activist John Ackerly, Tashi's fears are well founded.

"There is no real reason for this railroad to be built other than to provide for the Chinese military and settlers," he says. "There will be a few benefits for some parts of the Tibetan population but the sad thing is that this will continue a tradition of building large infrastructure projects that the Chinese population needs, while ignoring the real needs of the broad population of the Tibetans."

Another train rolls into Golmud station packed with migrants heading for Lhasa. Most are peasant farmers fleeing a life of poverty on the over-crowded plains of central China.

There are farmers like Lao Zhang. With a heavy bundle perched on his shoulder, he is heading for the bus station. From Golmud he still faces a gruelling two-day journey across the mountains to Lhasa - but it is worth it.

"There are lots of opportunities in Lhasa," he says. "I can get work there, maybe start my own business.

"Hopefully I can make some good money."

For Tibetans, the fear is that once the railway is finished this steady trickle of migrants will turn into a flood.