Drivers who use one of Cornwall's biggest junctions - which is undergoing improvements - need re-educating to use it safely, a project manager says.
Chiverton Cross roundabout, on the A30 near Truro, is undergoing a £3.8m programme of works.
Road users and people working nearby reported seeing drivers in difficulty and unsure which lanes to use.
Cornwall Council project manager Peter Swain said lanes had changed and drivers needed to pay attention.
Up to 50,000 vehicles a day negotiate the roundabout.
Cornwall Council said the improvements were designed to reduce delays facing motorists by easing congestion.
The works, which began last May, include extra approach and exit lanes, resurfacing and new signs.
Blaine Gilbert, who works at the nearby Chiverton Arms pub, said that he was not sure if it was going to reduce any problems in the area.
He said: "Drivers are still not sure which lane to go in."
Jim Geach, from Camborne, who operates a fleet of mini-buses, added that he believed a flyover would be the best solution.
The former county councillor said of the current works: "I don't think this scheme answers that."
Mr Swain, the council's major highways project manager, admitted that drivers were "probably confused" because the layout of lanes had changed a number of times.
He said: "There will be a period of time now where drivers need to take note of the signs, take note of any markings and get into the appropriate lanes as early as possible."