A young steam engine enthusiast was crushed to death after riding on an engine with his father in an "incredibly tragic" incident in County Durham, a inquest heard.
Karl Doran, seven, was volunteering at the time with his father Phillip at Beamish Museum, Stanley.
The father and son, from Darlington, had been driving a vintage steam roller around the open air attraction for visitors to see and had attached a trailer to the back.
But as Karl was standing on the tow bar as his father drove the engine, a position described in the inquest as a dangerous place to be, he came off and was crushed by the 1.5 tonne trailer.
Detective Chief Inspector Victoria Fuller, from Durham Constabulary, said the pair had been helping other volunteers work on the engines before setting off around the site in July last year.
She said Karl had been seen sitting on the tow bar by members of the public and that his father had asked him to join him in the engine after he began to drag his feet.
"Mr Doran became aware of the trailer rocking and he then realised that Karl was no longer on the engine," she said.
"He noticed Karl lying about 15-20 feet behind the trailer on the road. He was not responsive and there were no signs of life."
The inquest at Crook Civic Centre, County Durham, was told that the museum had not dealt properly with the risk assessment of towing trailers and the carrying of passengers and children.
Victoria Wise, from the Health and Safety Executive (SHE), said Beamish was aware that children would ride on the engines but that they relied on the competence of the drivers.
"Riding on a draw bar is a dangerous place to be: every year there are numerous accidents in agriculture where people are riding on draw bars," she said.
"We would never allow a child or an adult to ride on a draw bar of a machine.
"Riding on the bar itself puts you between two pieces of moving machinery and it's not designed to carry passengers."
As a result the HSE issued Beamish with an improvement notice, which they took action on, but their investigation is still yet to fully conclude.
After instructing the jury to deliver a verdict of accidental death, Coroner Andrew Tweddle said it was a tragic case which no one would have expected.
Richard Evans, director of the museum, said the safety of their visitors was their top priority and they wanted to exceed any standards that were out there and be an example of best practice.