Holding a flashlight, Cheng started his routine security check before departure. His assistant driver Ma Xinsheng was busy adding water to the boiler, while stoker Dai Yanjia poked a shovel into the furnace to check on the fire.

A steam locomotive is usually operated by four people: a driver; an assistant driver; a stoker, who is responsible for power supply; and a flagman, who gives departure and stop signals at the end of the train.

"If you want to be a driver, you have to start as a flagman, which is the most tiring job of all. Then you move up to stoker and assistant driver. It's taken me eight years and has required a huge amount of practice," Cheng said.