Forth Road Bridge main cable project, South Queensferry, Scotland

Forth Road Bridge main cable project, South Queensferry, Scotland
Project Information
  • Client: Forth Estuary Transport Authority
  • Principal designer: AECOM
  • Principal contractor: C Spencer
  • Contract value: £11.2 million

About the project

The Forth Road Bridge is a vital link in Scotland’s road network. Opened in 1964, it carries around 24 million vehicles each year, as well as pedestrians and cyclists.

When reports of corrosion found on similar (but older) bridges in the US prompted an inspection in Scotland, the results gave great cause for concern. Extensive corrosion was found not only on surface wires but right down to the centre of the cable, and some cables were broken. Unless deterioration was halted, future traffic restrictions were likely.

A dehumidification process developed in Japan for new bridges was used to stop the corrosion. The cables were wrapped in airtight sheathes, and very dry air injected into the voids between wires. It is the first time that this technique has been used on a bridge as old as this.

Gaining access to the cables was a challenge, but the contractor came up with an access platform that could climb the cables without workers having to leave the safety of the platform. Three of these platforms were built for the job.

Successful completion in December 2009 was the result of great technical skill, delivered through close cooperation between the client and its partners. It has ensured that this iconic and strategically important bridge is secured for generations to come.

Judges' comment

"Technical ingenuity combined with great team work."

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