The Qinghai-Tibet Railway, the world's highest rail line, is running safely and in stable condition two months after winter descended on the Qinghai-Tibet Plateau.

"Our inspections have shown that the track bed is in stable and accountable condition. There have been only minor changes as the ground has frozen, which the design allows for," said Xu Yongshuang, deputy manager of the Qinghai-Tibet Railway, as quoted by Xinhua News Agency.

Signals and snow melting equipment along the line are all operational, he added.

Winter safety has been a key concern for the railway. Some 1,100-kilometres of the track are at altitudes above 4,000 metres, and the line crosses 550 kilometres of permafrost. Temperature changes could potentially alter the shape of the permafrost, threatening the stability of the rail bed and raising the possibility of accidents.

Xu said problems like unstable permafrost could arise in the railway's first winter. To offset the likelihood of an accident, the company has drafted emergency plans in case problems occur on the rail line during the winter months.

For example, spare locomotives positioned at major railway stations along the line can be dispatched to replace malfunctioning locomotives in one or two hours. Local governments will also be involved in any rescue effort in the event of an emergency.

Since October, railway departments have stepped up inspections and maintenance along the line to ensure trains run safely across the world's highest plateau.

Wang Yingxian, a senior railway engineer at the Northwest Research Institute under the China Railway Engineering Group, told China Daily that the 550 kilometres of track sitting on top of frozen ground were constantly being monitored with the aid of electronic sensors.

"The tracks on frozen ground are under automatic inspection, which means we receive around-the-clock data on weather and ground temperature," Wang said.

The Northwest Research Institute is based in Lanzhou, in Northwest China's Gansu Province. The institute is the only organization in the railway system that studies permafrost on the plateau.

Before this year, observation teams surveyed the tracks three times a day, even when temperatures dipped to -30 C, he said.

At present, teams still check for subsidence and deformities in the rail bed.

"There are more than 70 monitoring teams along the line who work together to inspect the rails sitting on permafrost every 15 days," he said.

The Northwest Research Institute has been gathering data about permafrost conditions on the Fenghuo Mountain for the past 45 years, providing statistics for the design and construction of the Qinghai-Tibet Railway.

"The Qinghai-Tibet Railway has many measures in place to protect the frozen ground," he said.

For example, engineers have used stone slabs to build embankments that cool without breaking up. They have also thrust steel tubes into the ground along some parts of the route to transmit heat from beneath the icy surface.

Bridges were built where the permafrost was unstable to minimize the railway's influence on the environment.