Industry standards should be reviewed after fatigue and corrosion caused high-speed trains to be phased out, the rail regulator has found.
Cracks were found in more than 180 Hitachi trains operated by the Great Western Railway (GWR) and London North Eastern Railway (LNER) last year.
The Office for Rail and Roads (ORR) said the damage was partly due to the trains being corroded by salt in the air.
Hitachi Rail said it has “taken reasonable steps to prioritize safety”.
In May 2021, the withdrawal of the damaged Hitachi Series 800 and 385 trains resulted in a week of delays and cancellations for travelers.
The operators affected were Great Western Railway, London North Eastern Railway, TransPennine Express and Hull Trains.
Cracks were also noted upon examination of ScotRail’s Class 385 and Southeastern’s Class 395 trains.
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The ORR investigation revealed that the trains’ construction was to existing standards, but that corrosion cracking was found on lifting points – which allow the wagons to be lifted during maintenance work – which are attributed to the use of a certain type of aluminum which is contaminated by salt in it the air was corroded.
Fatigue cracks were said to be caused by the “cables being subjected to greater stresses than the original design allowed for due to the tensile movement”.
It added: “It is not yet known for certain why this happened, although possible factors include wheel wear and track design.”
The trains first entered service in 2017.
The further work recommended by the ORR was carried out to identify the reasons for the cracking in the rolling stock.
It has been assured that “no safety failures and trains have functioned as advertised” since they were put back into service.
Ian Prosser, ORR Chief Inspector of Railways, said Hitachi Rail and other operators had “robust plans in place to ensure the right safety issues are managed”.
“Our review provides a clearer picture of the issue and we will continue our oversight to ensure work progresses to agree on the permanent solution and follow up on our recommendations,” he added.
“It’s important that the entire industry works together to learn lessons from what happened.”
Hitachi Rail has proposed a plan to replace and modify affected parts over a six-year period to minimize the number of trains out of service at any one time.
In a statement, the company said the report confirmed that “all Hitachi trains meet the relevant standards and that we have taken the appropriate measures to prioritize safety and maintain train availability.”
“The proposed technical solutions outlined in the report are currently being considered by all partners,” he added.
“We are working together to finalize the plan for their implementation, always prioritizing safety and train availability to support consistent passenger service.”
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