Fatal Mid-Wales train crash: Accident investigation branch give update

The failure of an automated train safety system could have contributed to a fatal collision between two passenger trains near Talerddig, Powys, according to an update from the Rail Accident Investigation Branch (RAIB).

The incident, which occurred on 21 October 2024, claimed the life of one passenger and left four others with serious injuries, with eleven more requiring hospital treatment.

The accident occurred at around 19.26 on the Cambrian Line, approximately 900 metres west of the Talerddig passing loop.

Transport for Wales’ westbound Train 1J25, travelling from Shrewsbury to Aberystwyth, collided with eastbound Train 1S71 en route from Machynlleth to Shrewsbury.

In addition to the passenger fatality, four people suffered serious injuries, while eleven others required hospital treatment for various injuries.

Both trains sustained significant damage to their leading carriages, although neither train derailed.

Initial Findings

After receiving notification of the incident at 19.45, the RAIB dispatched investigators to the scene.

Working alongside the British Transport Police, the Office of Rail and Road, and the involved railway companies, RAIB teams examined the crash site, the equipment on board both trains, and the surrounding area.

The site was released back to Network Rail on October 23 to begin repairs, with the damaged trains removed by October 25.

The two 2-car Class 158 diesel multiple units involved were equipped with advanced safety systems, including a wheel slide protection mechanism, similar to anti-lock braking systems used in cars, and an automatic sanding system.

This sanding system is designed to release sand on the track when low adhesion is detected, providing the wheels with additional grip.

However, an inspection revealed that the sanding hoses on Train 1J25 were blocked and unable to dispense sand during the braking process, a malfunction that left the wheels unable to gain the traction needed to stop safely.

Sequence of Events

According to RAIB’s preliminary analysis, Train 1J25 was intended to stop at the Talerddig loop to allow Train 1S71 to pass on the single-track line.

Onboard data from Train 1J25’s recorder indicates that the driver initially applied standard braking as the train approached the loop, with an emergency brake activation recorded shortly afterward as the train’s wheels began to slide.

The wheel slide continued as the emergency brake was engaged, with no sand discharge to increase traction. Train 1J25 eventually passed through the loop without stopping, rejoined the single track, and travelled an additional 900 metres before colliding with Train 1S71.

Conflicting Speed Data and Adhesion Levels

While the exact speed at the point of impact is still under review, preliminary RAIB data suggests that Train 1J25 was moving at speeds between 24 km/h (15 mph) and 39 km/h (24 mph), while Train 1S71 was estimated to be travelling at around 10 km/h (6 mph) in the opposite direction.

Investigators are further analysing speed data as part of the ongoing investigation.

To understand the conditions affecting braking, RAIB conducted measurements along the rail from the Talerddig loop to the collision site.

Findings indicate that the wheel/rail adhesion levels were notably low, which likely exacerbated the difficulty in stopping, particularly on the descending gradient from the loop.

Broader Investigation Scope

The RAIB’s investigation is examining a range of possible factors contributing to the incident, including:

• Driver Actions: RAIB is reviewing the actions of both drivers to understand any human factors at play.
• Braking and Safety Systems Performance: In addition to the sanding system, other braking and wheel slide protection functions on Train 1J25 are under scrutiny.
• Adhesion Management Policies: Both Transport for Wales and Network Rail’s policies for handling low adhesion on the Cambrian Line are being reviewed, with attention to whether the known risks were effectively mitigated.
• Risk Assessment Practices: The processes in place to evaluate and manage overrun risks, particularly on single-track lines with passing loops, are also being considered.