A stretch of railway across China’s Inner Mongolia has become the testing ground for a breakthrough in heavy freight transport, as engineers demonstrated a record-breaking convoy of coal trains operating as a single, digitally coordinated unit, Xinhua reports.

In early December, seven heavy-haul freight trains, each carrying 5,000 tonnes of coal, moved in tightly synchronised formation along the Baotou–Shenmu line, a key corridor linking Inner Mongolia with neighbouring Shaanxi province. Together, the convoy transported 35,000 tonnes, Xinhua says - the largest load ever handled in this way, without the trains being physically coupled.

The trial replaces traditional steel couplers with a high-speed wireless control system that allows trains to operate in close formation while remaining mechanically independent. Using real-time data links, the system synchronises speed, braking and acceleration, enabling multiple trains to behave as a single entity before separating automatically at their destination.

The project, led by CHN Energy Baoshen Railway in partnership with the China Railway Signal & Communication Research & Design Institute, is designed to push beyond the long-accepted physical limits of rail freight. Conventional heavy-haul operations face constraints from mechanical stress and safety spacing, which cap the length and frequency of trains on busy routes. By contrast, the digitally linked convoy sharply reduces the required distance between trains and avoids the damaging forces generated in ultra-long, mechanically coupled formations.

Engineers estimate that the technology could lift carrying capacity on the Baotou–Shenmu line by more than 50% without laying new track or extending platforms. The railway already handles about 180mn tonnes of freight a year, much of it coal from nearby mines, making efficiency gains particularly valuable.