A report by the Rail Accident Investigation Branch has found that a major freight train derailment near to Lincoln was caused by a buckle in the track on the hottest day of the year.
Investigators also noted that the under-resourced maintenance team in the area may also have been a factor in the incident, and has recommended that Network Rail improves track assessments.
The freight train, conveying 22 empty diesel fuel tank wagons derailed on a track buckle near to Langworth on the afternoon of June 30, 2015.
The train and the first ten wagons ran over the buckle before the 11th and following nine wagons derailed, four of them overturned, rolling off the track.
While no one was injured in the incident, there was a significant fuel spillage and extensive damage was caused to the train and the infrastructure. The line was closed long into the night.
The investigation found that the track buckled on the hottest day of 2015 when the rails suffered thermal expansion.
Investigators stated: “The buckle started at a point where there was an existing misalignment in the track; a feature which reduced its resistance to buckling.
“The buckle increased under the train because its permitted speed was too fast for the vulnerable condition of the track and the rail temperature on the day.
“Underlying the accident was a lack of appreciation of the vulnerability of the track to buckling. The under-resourcing of the maintenance team, leading to the continual reprioritisation of maintenance tasks, was also a possible underlying factor.”
Following the investigation, RAIB made four recommendations to Network Rail:
- Improved assessments of the vulnerability of track to buckling on the basis of more accurate data about its ability to withstand thermal expansion.
- Ensure a more consistent interpretation of risk factors is included in the calculation of rail temperatures at which mitigation measures, such as speed restrictions, should be applied.
- Improved local resourcing for track maintenance
- Managerial oversight of the process of reprioritising or cancelling maintenance tasks