No 20 platform of the Shanghai Hongqiao Railway Station, the busiest in China, receives tens of thousands of passengers every day during the Spring Festival travel season. [Photo/WeChat account: hongqiaoshangwuqu]

A total of nine stewards work at the platform, three of whom are on duty at any given time. They move back and forth in a hurry among carriage doors, elevators, and transfer channels to ensure passengers'safety.

It's the 7th year that Zhang has worked at the platform. His experience has enabled him to figure out the regular patterns of boarding and deboarding the trains.

So, as soon as a train pulls in, he will run over to whichever carriage has more passengers getting on or off to guide them.