The collection includes the 150-year-old Hetton Colliery loco

The �11m Locomotion, in Shildon, County Durham, was opened by prime minister Tony Blair in 2004.

Figures from Sedgefield Borough Council show the site has since attracted more than 350,000 visitors and contributed �4.2m to the region's economy.

The museum is based at the first departure point for the Stockton and Darlington Railway in 1825.

Before the museum opened, it was expected to generate about �1m a year.

'Flagship attraction'

But new figures show the site, which supports 72 jobs, is "greatly exceeding" expectations.

Louise Davis, head of tourism at regeneration agency One NorthEast, said: "Quality visitor attractions like Locomotion, which won recognition at the recent North East England Tourism Awards, help raise County Durham's profile as a visitor destination."

Melanie Sensicle, chief executive of the County Durham tourism partnership, added: "These results prove that Locomotion is certainly a strong part of what North East's tourism has to offer.

"It is a flagship attraction that adds to the ever-strengthening North East tourism product and is clearly a big fish in the County Durham tourism pond."

Since it opened, Locomotion has won or been nominated for 15 county, regional, national and international awards.