The Rail Accident Investigation Branch (RAIB) says the drama took place on June 12 at Margam Yard on a siding used for wagon maintenance.
The railworker was carrying out shunting work that morning when two freight wagons were being coupled together after repairs.
He was between the wagons and, as they were moved together, was crushed between buffers.
A preliminary RAIB examination found that the man had been out of sight of his two workmates at the time.
The RAIB will publish its final findings after its full investigation. They will be publicly available.
RAIB The Rail Accident Investigation Branch is the UK’s independent railway accident investigation organisation. It looks into incidents to improve safety, not to establish blame. Investigators are independent and are focused solely on safety improvement.
Photo: The wagons involved in the Margam accident. Pic www.raib.gov.uk