A21 widened near Tunbridge Wells as ancient woodland lost
Construction work is to get under way to turn a 2.5 mile stretch of road in Kent from a single to dual carriageway despite conservationists' objections.
Campaigners worked for years to get the £69m scheme for the A21 near Tunbridge Wells approved.
But groups including The Woodland Trust objected to the destruction of 22 acres of ancient woodland.
Highways England say 44 acres of new woodland will be planted and managed for 25 years in mitigation.
The widening of the stretch of the busy A21 London to Hastings road was given final approval by the Highways Agency last May following a public inquiry in 2013.
The Freight Transport Association said the new road would be a huge improvement on the current bottleneck.
"It costs about £1 a minute to run a lorry so being sat in congestion is bad for business," said spokeswoman Natalie Chapman.
"It is also bad for air quality so we should see some real environmental benefits from this."
Woodland Trust spokesman Richard Barnes said the decision was taken to widen the road and lose the ancient woodland without looking at options such as tunnelling or improved public transport.
"One of the woods had 1,000 different types of fungi in it so a real wealth of wildlife has been lost," he said.
"This is irreplaceable habitat. It's been around for hundreds, if not thousands, of years."
Highways England said the loss of ancient woodland along the A21 was unavoidable.
"We have coppiced trees along the route so that they are ready for translocation into the nearby 'receptor areas'," it said.
"In total, 9 hectares (18 acres) of woodland have been coppiced.
"Our woodland translocation is one of a combination of woodland creation measures that we will use to create 18.1 hectares of woodland in areas bordering the new dual carriageway. "