The Tamar's place in engineering history is assured

Richard Fish, project manager

Following the opening, chief engineer for the New York State Bridge Authority, Bill Moreau, visited the Tamar project to study the work first hand.

He said: "Suspension bridges are very difficult to work on as engineers have to consider weight and balance at all times.

"Tamar is fascinating because three lanes have been turned into five with only a small increase in weight."

New York has many aging suspension bridges and Mr Moreau and his team are looking at revamping them or knocking them down.

Mr Moreau looks after two suspension bridges, one of which is the Mid Hudson Bridge which needs greater traffic capacity.

Brooklyn Bridge is a world-famous suspension bridge

New York City has 38 major bridges, including the world famous Brooklyn, Manhattan and George Washington bridges, and four of them are owned by the Mass Transit Authority.

Its principal research engineer, Dr Are Tsirk, has also been keeping an eye on the Tamar project to consider whether similar techniques could be used on the Bronx Whitestone bridge.

Cornwall's assistant director of planning, transportation and estates, Richard Fish has been to New York to lecture on the project.

"Engineers the world over have been watching this project closely because it is absolutely unique in bridge technology.

"Now the Tamar's place in engineering history is assured as the world's first suspension bridge to be widened using cantilevers."

The bridge first opened in 1961 with three lanes for traffic and a central span of 335m (1100ft).

When it was opened, it was the longest suspension bridge in the UK and today is still jointly owned by the people of Plymouth and Cornwall.

Although up to 40,000 vehicles a day used the bridge during the three year project, the scheme caused tailbacks for motorists.