At 19:53, five tank wagons on the freight train conveying cement powder from Clitheroe, Lancashire, to Mossend, near Glasgow, derailed. A number of wagons were damaged and there was significant damage to the track and to the bridge over the River Petteril. This resulted in closure of the routes from Carlisle to Newcastle- upon- Tyne and to Settle for seven weeks. No one was injured.
The derailment occurred because one set of wheels on the ninth wagon in the train stopped rotating during the journey. These wheels had stopped rotating up to 55 miles (88 km) before the derailment and continued to slide along the railhead causing considerable damage to the profile of the wheel treads. This meant that the wheels were unable to safely negotiate a set of points just before Petteril Bridge Junction, damaging them and causing the ninth wagon to become derailed. Five of the wagons derailed due to the consequent track damage and two of them fell off the side of the bridge where the railway crosses the River Petteril. The ninth tank wagon was ruptured and landed upside down in the river, although very little of the cement powder was spilled.
The initial wheel slide was probably the result of a normal brake application made in low adhesion conditions that were not abnormal for the route at the time of year. The wheel slide continued because the adhesion between the wheels and the rails was then insufficient for the wheels to restart rotation.
The non-rotating wheels were not identified by the signallers on the route, nor by the train driver or any engineered system, meaning that the train was not stopped before it reached Petteril Bridge Junction.
RAIB recommends that the railway industry undertake work to understand the specific risks to freight trains in low adhesion conditions. It has also identified one learning point for signallers, reminding them of the circumstances in which they should stop trains for examination.