Two rail workers who were killed near Port Talbot had been using a petrol-engined tool and were not aware of the approaching train, early investigations have found.
The Rail Accidents Investigation Branch (RAIB) said Michael Lewis and Gareth Delbridge were doing scheduled maintenance on the Margam Moors lines which were open to traffic on 3 July.
The driver sounded his horn and applied the emergency brake.
A third worker was almost struck.
The RAIB said Mr Lewis, 58, of North Cornelly, and Mr Delbridge, 64, of Kenfig Hill, were working with four others on a set of points, using a petrol-engined tool and at least one of the workers was wearing ear defenders.
CCTV images suggest they did not become aware of the train until it was very close to them, travelling at about 50mph (80km/h).
Workers on the adjacent line became aware of the train and tried to warn their colleagues as it passed them.
The RAIB's investigation will identify the sequence of events that led to the accident and consider:
- what might have influenced the actions of those on site
- the protection arrangements that were in place
- the planning of the work and the implementation of Network Rail's standard for keeping people safe on or near the line
- any relevant underlying management or organisational factors
Coroner Colin Phillips has previously adjourned the men's inquests at Swansea Coroner's Court for a review in six months.