The government has announced it is to spend £30m on a link road between St Austell to the A30.
Eden: Free for walkers and cyclists
The aim is to ease congestion around Stenalees, Penwithick and Bugle, partly caused by the Eden Project.
Work will start on the bypass, which was first proposed in 2001, in 2007.
Transport Minister David Jamieson admitted it had taken time, but said the plans were now in place.
He said: "What we have now is a decided route that Cornwall wants to use.
"I think all the partners involved with this realise there is a preferred route, although I have to say it does have to go through the public inquiry first.
"But nevertheless the government has now recognised the enormous importance of this road."
The Eden Project, which opened in 2001 in a disused quarry near St Austell, atttracts more than £1.8m visitors a year.
Eden is free to those who walk there or arrive on bicycle, but 82% of those visitors arrive by car.
Spokeswoman Brier Scudamore said that those walking had increased from about 200 to more than 800 this year.
She said: "We would like to see access improved for all methods of transport, not just cars.
"But this is great news for central Cornwall because the traffic must put some people off."