The Rail Accident Investigation Branch has released an interim report into the crash between two Transport for Wales Class 158 trains in Mid-Wales.

The accident happened on the 21st October 2024 at Talerddig loop in Powys.

1J25, the 1831 Shrewsbury to Aberystwyth Transport for Wales service, collided with 1S71, the 19:09 Machynlleth to Shrewsbury TfW service.

One passenger sadly died, and four others were seriously injured in the accident.

Neither train derailed, but both leading carriages were significantly damaged.

1J25 was due to stop in the loop to let 1S71 pass it; the reason for this was that the latter was travelling up a steep gradient into the loop.

1J25 slid around 1,080 metres beyond its stopping point before colliding with 1S71.

1S71 was made up of 158824 and 1J25 was made up of 158841, both owned by Angel Trains and operated by Transport for Wales.

The RAIB investigation found that during the night of 19/20th October, 158841 had a Fuel Point Examination at Machynlleth Depot, which included refuelling of the train and a check of the train’s safety equipment, which includes the automatic sanders. The unit then operated on various routes in Wales before finishing at Shrewsbury, where it was planned to run empty to Crewe Maintenance Depot.

However, due to disruption, the unit was sent to Chester station to be stabled there overnight.

On the 21st October, a train driver prepared the unit for service, but because the train was parked next to a platform, the driver couldn’t access the train’s underframe, and couldn’t use the sander test button.

During its investigation, the RAIB found light and intermittent contamination on the railhead, and these are still being analysed in a lab.

Network Rail operates various RailHead Treatment Trains in the autumn season, and this ran successfully on the 20th October, the night before the accident. This train treated the various single lines around Talerddig as well as both tracks in the loop.

At this location, only water jets are used to clean the track, the RHTT can also use a gel but this was not used on the Cambrian line.

On investigation, the RAIB found that the sanders on 158841 had become blocked. No defects were reported by drivers on the 20th and 21st October. But this fault would have prevented sand from being ejected onto the rails to help stop the train.

The RAIB also found that the pipes were blocked at the outlet end and no sand was built up behind the blockage.

The investigation has deemed that the blockage came from external sources and DNA testing has found leaves and debris from ash, acer and cherry trees.

There was no evidence that the emergency sander was activated during the accident. Upon testing, the sander healthy lights were not illuminated, which was traced to a tripped circuit breaker which provides a current to the system.

The circuit breaker is installed in the roof panel above the driving desk, which sustained damage in the accident.

After closing the circuit breaker, both lights illuminated, and both cylinders fired and delivered sand when the plunger was pressed.

Each sander delivered 4kg of sand in around 30 seconds.

The RAIB says that this is an interim report and a full report will be released in due course.