Improved journey times are promised in an environmental study to mark the start of a 12-week public consultation on widening the M25 in Kent.
The M25 is to be widened near the Dartford stretch
Work on the £66m scheme to widen the motorway from three to four lanes in each direction near Dartford is due to start next summer.
The Highways Agency is asking the public to comment on the environmental impact of the scheme by 14 February.
The agency has said impact on protected species will be minimised.
Alternative habitats will be created and the impact of the road reduced by planting traditional British plants alongside the motorway, it said.
The work will include widening the road between junction 2 and junction 3 in each direction, and widening the southbound carriageway between junctions 1b and 2 from two lanes to three.
The environmental statement will be on public display on 7, 8 and 9 December in Swanley and Sutton at Hone, where Highways Agency staff will be on hand to answer questions.
"We want to hear what the public has to say about this scheme in the light of the environmental assessment," said project manager John Martin.
Copies of the statement are also available at local libraries and council offices and a summary is on the Highways Agency website.