"Our work seems very simple. We just try to reduce the chances of trains making emergency stop to ensure the safety of both the railway operation and people living along the railways," said Gou, who used to walk 20 km each day to patrol the railway line.

However, things are not always so simple. Guo has had quite a few breathtaking experiences. One rainy day, a man in his 70s carrying a bike attempted to cross the rail tracks directly to avoid the water-logged underpass when a train was approaching.

"I felt so worried that I rushed toward the old man and pulled him off the track just before the train passed," Gou said. After dealing with such an emergency, Gou realized how important his work could be.

By the end of 2018, China's railways spanned some 131,000 km, from plateaus and plains to deserts and cities. High-speed lines in the country have reached 29,000 km, accounting for two-thirds of the world's total.