Wang Fuchun's black-and-white photographs reveal the lives of passengers on trains. [Photo by Wang Fuchun/provided to China Daily]

During the mid-1990s, four or five diazepam tablets couldn't get him into sleep. However, the rhythmic rumble of the old-style trains was able to cure his chronic insomnia, he says.

Yet, Wang's devotion sometimes led to misunderstandings.

"When I wander along the aisle and look around, people will sometimes become defensive. Once a passenger mistook me for a thief and turned me over to the police. I had to show my work credentials and explain what I was doing over and over again before they would release me," he recalls.

As the Chinese people pay more attention to privacy nowadays, taking photos of strangers has become even harder. Wang was even punched in the face in 2015 when taking pictures of a passenger in a high-speed train.

Another challenge Wang faces is that people rarely talk to strangers nowadays. Instead, they appear in his photos concentrating on their cellphones.