INADEQUATE maintenance practices were partly to blame for the derailment of a tanker train in Carmarthenshire in 2020, a report says.

Rail Accident Investigation Branch (RAIB) has released its report on the derailment of a train that was carrying 25 laden tank wagons when it came off the tracks near Llangennech, Carmarthenshire on on August 26.

Ten wagons derailed, spilling around 446,000 litres of fuel, causing major damage to the environment in an area which is both a site of special scientific interest (SSSI) and a special area of conservation (SAC).

The derailment occurred because one set of wheels on the third wagon in the train stopped rotating during the journey, the report says.

The wheelset had become locked, probably because of a defect in the braking system on the third wagon, arising from deficiencies in the design and maintenance of components.

This meant that the wheels were unable to safely negotiate Morlais Junction, near Llangennech, causing the third wagon to become derailed.


The 9.52pm service was travelling from Robeston, Milford Haven, to Theale, when it derailed at about 11.04pm. 

The National Wales:

RAIB made nine recommendations, which included:

  • The manufacturer of some of the braking system components to undertake a review of their design.
  • Organisations who carry out surveillance and certification of entities in charge of maintenance of rail freight vehicles to review their processes.
  • Improve the management of wagon maintenance on the railways in Great Britain.
  • Review technology and systems used to alert traincrew, signallers and railway control offices to wagon defects that may lead to derailment.
  • Review the arrangements for regulatory oversight of entities in charge of maintenance and certification bodies that are not based in the UK.


Chief Inspector of Rail Accidents Simon French said what happened at Llangennech was a "disaster". 

“The rail industry’s approach to the safe maintenance of freight wagons needs to improve," said Mr French.

"In this investigation we found that there were inadequate maintenance practices, and a failure to appreciate the importance of the correct fastening of the various components of the tanks wagons’ braking system.

“The majority of our recommendations following our extensive investigation of the derailment at Llangennech relate to improved maintenance processes for freight wagons.

"The widest ranging of these urges the freight sector, in conjunction with Network Rail, to develop a comprehensive programme of measures designed to promote the improvement of freight wagon maintenance in the UK.

“I would like to stress the importance of getting this right. It’s time that freight wagon maintenance practices were subject to careful examination and for the industry to think through the way that it can best deliver on its legal and moral obligation to present wagons that are fit to operate through the nation’s towns and cities."

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