Work has begun to ease congestion on the A120 near Bishop's Stortford.
Essex Highways is replacing the A120/A1250 Dunmow Road roundabout with a signal-controlled junction.
The A120 south of Birchanger and the M11 junction 8 slip roads (Stansted Airport) will also be widened.
Work on the project was originally due to start in 2018, but the project has since been re-designed after residents raised concerns.
The latest plan - dated December 2021 - features a 50mph speed limit and off-road routes for cyclists and pedestrians.
An Essex Highways statement reads: "The area around junction 8 of the M11 is increasingly congested.
"Planned developments north of Bishop’s Stortford and local growth planned in East Herts and Uttlesford will lead to an increasing amount of traffic using the junctions in the years ahead as London Stansted Airport continues to grow."
The scheme is set to meet forecast traffic demands until 2036.
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