An automated system that helps train wheels grip tracks failed on a train involved in a fatal crash in mid-Wales on 21 October, the Rail Accident Investigation Branch (RAIB) said.
The Rail Accident Investigation Branch said the westbound train involved in the head-on collision in Talerddig, near Llanbrynmair, in Powys was fitted with a system which discharges sand automatically via hoses when it detects that the wheels are sliding during braking.
This is intended to increase friction between the wheels and the tracks.
The RAIB said an inspection of the train after the accident showed that the sanding hoses on the leading vehicle of the train were “blocked and apparently unable to discharge sand”.