The Rail Accident Investigation Branch (RAIB) has issued its interim report (IR 1/2025) on the head-on collision that occurred at 19:26 on 21 October 2024 between two Transport for Wales services on the Cambrian line west of Talerddig passing loop, Powys. The document, released on 30 April 2025, sets out the evidence gathered so far and explains the work still to be completed before a final report is published.
Collision overview
- Services involved – Westbound train 1J25 (18:31 Shrewsbury–Aberystwyth) and eastbound train 1S71 (19:09 Machynlleth–Shrewsbury), both formed of two-car class 158 diesel multiple units.
- Casualties – One passenger died; four people, including the driver of 1S71, were seriously injured; a further 18 passengers sustained minor injuries.
- Speeds at impact – 1J25 was travelling at about 39 km/h (24 mph) and 1S71 at about 11 km/h (6 mph). Neither train derailed, but the leading vehicles suffered significant damage.
- Infrastructure impact – Exit-loop points were damaged; the Cambrian line reopened seven days later on 28 October 2024.
Provisional findings
The interim report attributes the primary cause to train 1J25 overrunning block marker MH 1078 after failing to stop in the Up Loop:
- Low wheel–rail adhesion – Damp rails, fallen-leaf contamination and a known low-adhesion zone contributed to poor braking.
- Sanding system defects – The automatic sanders on the leading vehicle of 1J25 were inoperative owing to electrical faults, incorrectly fitted orifice plates and blocked discharge hoses containing organic debris. These faults prevented sand delivery that could have restored adhesion.
- Emergency sanders – Healthy before departure, but not used during the incident.
- Signalling and operations – The European Rail Traffic Management System (ERTMS) intervened with full-service and emergency brakes, yet the train slid around 1,080 m beyond its intended stop. The signaller attempted to hold 1S71 at block marker MH 1081, but the collision occurred four seconds after the driver applied emergency braking.
Investigation status and next steps
RAIB will conduct further laboratory analysis of rail-head samples, complete testing of 1J25’s braking and wheel-slide protection equipment, and examine Network Rail’s and Transport for Wales’ low-adhesion management strategies, including the reliability of traction-gel applicators and rail-head treatment schedules. The Branch will also consider the design of the Cambrian ERTMS pilot and any underlying organisational factors.
Any safety recommendations will be made in the final report. RAIB reminds stakeholders that its investigations aim solely to improve railway safety; they do not apportion blame or liability.
