A DISUSED and degrading railway tunnel under the Forth Road Bridge has been made safe in an "unusual" project.

Amey, the Forth Bridges Operating Company, completed the infill work underneath the approach roads north of the bridge that originally formed part of the Dunfermline to North Queensferry railway line.

The line which spans 420 metres in length and 16.7 feet in height, provided a link to the ferry service until the opening of the Forth Bridge in 1890, before continuing in limited use for freight until 1954.

Two time capsules were also filled with local history and buried in the tunnel as part of the work.

Mark Arndt, Amey’s operating company representative for the Forth Bridges Unit, said: "This has been an unusual and interesting project where we’ve learned something new about the history of the area as well as gaining the satisfaction of making a disused tunnel safe.

“The team deserves particular credit for developing innovative solutions that maximised workforce safety while minimising the cost to the public purse and the impact on local communities.

“It’s a real measure of success that most local residents were not even aware this work was taking place, despite the tunnel emerging within metres of homes in North Queensferry.”

A timelapse of the work:

Both ends had been sealed off and the cuttings were filled in, meaning the only access points were through vertical shafts at each end.

Amey engineers carried out a structural inspection in February where they found parts of the tunnel were degrading and requiring maintenance to ensure safety.

Due to the limited depth of cover above the tunnel, a failure could potentially have had an impact on the roads overhead.

A decision was made to fill the tunnel with expanded polystyrene blocks built to resist the weight of rock and tunnel lining in the event of a failure.

Work was conducted at the north end of the tunnel and once offloaded, the blocks were passed down the shaft and transported down the tunnel on a sliding monorail system.

Once the body of the tunnel was infilled the access shafts were filled with concrete to seal the tunnel and prevent damage to the blocks, with work reaching a conclusion in late March.