RAIB's report into the head-on collision near Talerddig, Powys, published on 18 June 2026, sets out a systems failure rather than a single-point error. The accident happened at about 19:26 on 21 October 2024, when the 18:31 Shrewsbury to Aberystwyth service, train 1J25, collided with the 19:09 Machynlleth to Shrewsbury service, train 1S71, on Network Rail's Cambrian lines. Both services were operated by Transport for Wales Rail Limited. One passenger on 1J25 died. RAIB records four serious injuries across the two trains, including the guard on 1J25 and the driver of 1S71, with a further 23 people sustaining minor injuries. Neither train derailed, but both vehicles and infrastructure at Talerddig loop were extensively damaged. Andrew Hall, RAIB's Chief Inspector of Rail Accidents, said it was the first fatal train-to-train collision in more than 25 years.
The report explains that this part of the Cambrian route is mainly single track, with passing loops used to let trains travelling in opposite directions cross safely. Train 1J25 was due to enter the loop at Talerddig and stop within it so that 1S71 could continue past on the other line. Instead, 1J25 ran beyond its authorised stopping position, continued out of the loop and entered the single-line section already occupied by the approaching train. RAIB says the train travelled about 1,080 metres past where it should have stopped before the collision. At impact, 1J25 was travelling at about 39 km/h and 1S71 at about 11 km/h. The route remained closed until 28 October 2024.
RAIB found that the overrun was produced by three conditions acting together. First, wheel-rail adhesion on the approach to Talerddig was low. In plain English, the steel wheels had less grip on the rail than the braking plan assumed, although RAIB notes that the level was not unusual for that area in October. Second, the two sanding systems fitted to 1J25 did not provide the extra grip that might have altered the outcome. The report says the automatic sander probably failed because of electrical faults in its control circuit, while the manually operated emergency sander was not activated. Third, 1J25 approached the eastern entry to the loop at a speed that required a level of deceleration which could not be maintained with the adhesion available on the day.
Once 1J25 had passed its stopping point, the position worsened quickly. According to RAIB, the single line beyond the loop had exceptionally low adhesion and a steep downhill gradient. Even with the brakes remaining applied, the train did not slow as it ran towards 1S71. This is one of the report's clearest policy findings. RAIB says there were no engineered safeguards in place that would have prevented an overrunning train from entering an occupied single line. That shifts attention from train handling alone to infrastructure design, control logic and the way local risk is assessed.
The nine recommendations are aimed at those wider controls. Two go to the Rail Safety and Standards Board and rolling-stock owner Angel Trains, asking for stronger design, maintenance and testing arrangements for trainborne sanding equipment. For the industry, that is a direct signal that a safety-critical subsystem cannot be treated as dependable unless fault detection, inspection and assurance are robust. Network Rail receives several of the most consequential actions. RAIB wants it to revisit the assumptions that supported the use of simpler methods for assessing overrun risk on the Cambrian lines, taking account of this accident and newer industry standards. It also asks for better overrun protection in future versions of software-based train control systems. In practical terms, that means the control system should do more to contain the effects of a train that fails to stop where authorised.
A further recommendation to Network Rail concerns railhead treatment and seasonal adhesion management. RAIB says the company should improve wheel-rail adhesion conditions by applying a better understanding of how effective railhead treatment regimes are in practice. The report links that work to a previous recommendation made after the Salisbury accident in 2021, showing that low-adhesion risk remains an open cross-network safety issue rather than a site-specific anomaly. Transport for Wales Rail Limited is asked to review driver training in response to issues identified by the investigation. A separate recommendation says all on-train staff, whatever their job title, should have the knowledge and skills needed to assist during an emergency. In operational terms, that pushes the operator towards clearer competence standards not only for driving technique but also for incident response on board.
RAIB also calls on the Rail Safety and Standards Board to review the standards and rules governing passenger train interior fittings, with the aim of reducing injury risk in collisions. It adds a learning point on safety-critical communication, saying signallers and drivers need a clear shared understanding during operational exchanges. That is a narrow point on paper, but it goes to clear spoken confirmation in degraded or fast-moving situations. Hall said the lessons from Talerddig should support lasting safety improvements on the Cambrian line, across the rollout of the European Rail Traffic Management System and on the wider railway. RAIB's role is not to assign blame or determine liability. Its task is to identify what must change, and this report sets out a detailed programme of work for Network Rail, Transport for Wales, standards bodies and rolling-stock interests.