A council has said it may have "done things differently" during the construction of a major £205m road.
A report into the Broadland Northway near Norwich built by Norfolk County Council looked at a £20m overspend, contracts and road safety.
The 12-mile (19.5km) road fully opened in April 2018 and was originally called the Northern Distributor Road.
Martin Wilby, the county councillor in charge of roads, said: "We might have done a few things differently."
"But hindsight is clever for everyone," he added.
The report said that works related to Network Rail and utility companies were "sources of considerable cost increase and delay" and they should have been involved in the project at an earlier stage.
It also said there had there had been concerns with the incentives for contractors, and the types of contracts the council used with the construction company.
The report also suggested three roundabout designs that needed remodelling.
Conservative-led Norfolk County Council had already spent £130,000 to make changes to roundabouts to reduce crashes.
Mr Wilby said: "From this report and building our road we've learnt a lot and we'll use those lessons in our next major project."
But he added the road "benefits Norfolk and the east of England".