Great Western Coffee Shop

On 30 October 2017, train 6B13, which was carrying oil-based products from Robeston oil terminal, Milford Haven, to Westerleigh oil terminal, Bristol, caused extensive damage to railway infrastructure over approximately 25 miles (40 km). After the train had been stopped, at the entrance to Llangyfelach Tunnel near Swansea, the driver found that there had been a catastrophic failure of the braking system on one of the fully laden wagons.

The investigation found that one of the wheelsets on the damaged wagon had locked up and slid, causing severe wheel flats, before starting to rotate again. Impacts from the wheel flats subsequently damaged the rails as well as equipment mounted on the bogie, some of which partially detached and was dragged under the train, causing damage to track-mounted equipment. The wheelset had locked up and then started rotating again because an object became caught between one of the wheels and the adjacent brake block holder. This was most likely to have been one of the brake blocks, which had fallen off the wagon during the journey of train 6B13, probably due to the omission of key components when the brake blocks were replaced on 27 October.