The Forth Road Bridge will undergo eight months of roadworks while engineers replace its worn-out expansion joints.

The £9m project is due to begin in spring 2018 and last for up to eight months, with one of the two carriageways closed at a time and single lane of traffic in each direction on the opposite carriageway.

The replacement of the joints, which was originally scheduled for 2009, was delayed until the opening of the new Queensferry Crossing to avoid major disruption to traffic.

Once the new crossing opens to the public in May, the Forth Road Bridge will become a "public transport corridor" for buses and taxis.

The main expansion joints, which are built into the carriageway under the north and south towers, allow the bridge deck to expand and contract "in response to wind, traffic loading and temperature".

Built by German firm Demag AG, the joints are thought to be the largest and oldest of their kind in existence.

They will be replaced with a new modified version of the same type of joint.

While closures are in place, work will also be carried out on footway, cycleway and approach viaduct expansion joints.

Further work to replace the comb joints on the north and south approach viaducts and the nosing joints at the north and south side towers will also be undertaken.

Transport Scotland is expected to award the contract in August.

Mark Arndt, Amey's Account Director for the Forth Bridges Unit, said: "These joints have performed well and lasted longer than their designers originally anticipated.

"However, as moving parts, they are subject to wear and tear and have now reached the end of their service life."