5,665 gates, 4,862 stiles, 1,054 bridges: but who maintains the Yorkshire dales?

'I'll still be doing this on a mobility scooter,' says one of 100 volunteers who survey national park's 1,628 miles of paths

One of the many reasons Sally Williams loves the Yorkshire dales national park is because its dramatic landscape has been marked by centuries of human activity. "It's not like you get in America - a huge area of undiscovered land that nobody has ever trodden on," she says, standing near the entrance to an old limestone quarry. "It's an area where people have lived and worked for centuries, and you can see the evidence of that all over the countryside."

The 67-year-old former librarian is one of an army of nearly 100 volunteers who, every summer, undertake a survey of the park's 1,628 miles (2,620km) of public rights of way. The volunteers, mainly local retirees, walk every single path and bridleway, ensuring that the park's "infrastructure" - including its 5,665 gates, 4,862 stiles, 4,399 signposts and 1,054 bridges - is accessible, undamaged and safe.