Work is due to begin on a new �16m flyover on a roundabout in Swindon which it is hoped will cut congestion. The work at Commonhead Roundabout near the town's Great Western Hospital will mean traffic heading along the A419 to the M4 will not use the roundabout.
The Highways Agency says there will be "minimal impact on traffic" during the work, which will last until late 2006.
A second bypass on the A419, which could be built near Blunsdon, is subject to a public inquiry.
Minister for Roads, Dr Stephen Ladyman, said the Commonhead flyover would help motorists.
"The new flyover will reduce congestion and improve journey times and safety. I am delighted work will soon start on this important scheme."