A large section of the A30 in Cornwall is to remain a single carriageway, the Highways Agency has confirmed.
Plans to make it a dual carriageway between Carland Cross and Chiverton Cross, near Truro, have been proposed for several years.
The agency said plans would have to be re-drawn because of the length of time since the original design was started.
It added that government policy now discouraged any new building in open countryside.
