A disused railway tunnel underneath the approach roads to the Forth Road Bridge has been made safe with giant polystyrene blocks.
It was part of the Dunfermline to North Queensferry railway line, providing a link to the ferry until the opening of the Forth Bridge in 1890. It continued to be used for freight until 1954.
Amey engineers carried out a structural inspection in February 2016, finding that parts of the tunnel were degrading and in need of preventative maintenance.
The unusual feat of engineering uses lightweight expanded polystyrene (EPS) which can be easily removed if the tunnel ever needs to be reopened.