A passenger train heading towards Swansea hit a trolley left on the tracks while travelling at 123mph. The industrial trolley had been left during maintenance work, a Rail Accident Investigation Branch (RAIB) found.
The Great Western Railway service was speeding through Challow, Oxfordshire, on its journey from London Paddington to the Welsh city.
The train was damaged and the trolley was destroyed, but no-one was injured in the collision, which happened shortly after 6am on October 21 last year.
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The train was the first to pass through the area following overnight maintenance work. The trolley - which weighed around 106lb (48kg) - was left on the tracks possibly because Network Rail workers failed to correctly follow processes for permitting the resumption of trains, and there were also "weaknesses" within the system, the RAIB said.
Investigators also found that the train was allowed to travel too fast after the accident, given the damage to equipment underneath it. After being inspected, the train reached up to 85mph as it was driven to Swindon, where the service was terminated.
Damage to brackets protecting the train's wheels meant it should not have been driven faster than 40mph under regulations, the report stated. The RAIB made five safety recommendations to Network Rail.
Chief Inspector of Rail Accidents Andrew Hall said: "Systems and processes designed to detect any equipment left on the track before lines reopen after maintenance work should not be reliant solely on human performance in the middle of a dark night.
"There are technological solutions which can assist with addressing this issue, and this accident is an example of an opportunity missed."
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