A "large proportion" of the one million trees planted as part of a £1.5bn roadwork scheme have died.
The trees were part of the A14 upgrade between Cambridge and Huntingdon, which was completed last year.
But in a Cambridgeshire County Council agenda it was revealed many had "died off" and were being replaced.
Highways England, which maintains the road, said more than 400,000 trees and shrubs have been removed and replaced by 866,000 new ones.
A spokesperson said: "We expect some trees and shrubs will fail to flourish, which is why we carry out regular checks."
The agenda, for a council highways and transport committee meeting on 9 March, said: "Whilst there have been one million trees planted as part of the scheme, a large proportion have died off and are currently being replaced by [Highways England's] contractor.
"Young saplings are used rather than more mature specimens as the rate of success is known to be much greater."
The document said there was "concern locally" the saplings would "take some time to provide noise mitigation".
It said "whilst trees are not known for providing this mitigation", the community were keen to fund more mature specimens, which "may prove challenging with the health and safety requirements associated with the operation of the A14 and work required".
A Highways England spokesperson said: "We delivered the new A14 to the highest environmental standards, and this included how we work when planting across our schemes.
"As part of any scheme, we regularly monitor how successful planting has been with an experienced and qualified ecologist.
"We are now replacing those trees and shrubs and will continue to monitor the success of planting across the A14 scheme."