It involves young men hanging onto, running alongside, climbing over and dancing on trains.
Photographer Marco Casino won the 1st prize at the World Press Photo Multimedia Contest recently, for his short film that looked at the lives of its participants.
Participation in the risky activity isn't huge, but young men are increasingly getting involved.
The documentary film is centred on Katlehong, a multiethnic district where all of South Africa's eleven official languages are spoken.
The trains run through the township, and are a key source of jobs, as well as connecting the economically disadvantaged area with the rest of the country.
Twenty years on from the ending of Apartheid, young people are using the trains as a way to express themselves, filming and uploading clips onto YouTube.
Almost all riders are male, and under 25, with groups naming themselves and working together to get footage.
However, it's incredibly dangerous, leading to numerous serious injuries, and there is now a task force dedicated to stopping it.
