The long-awaited A47 road scheme was initially going to be delivered by Galliford Try but was held up in the courts and was retendered last year to seek better value.
The upgrade will deliver a new 1.6km free-flow link road connecting the A11 northbound to the A47 eastbound via two new underpasses, plus a second 1km local link road.
Skanska will also construct a new road bridge, two new junctions, footbridge installation, and widen an existing link road to ease congestion and improve journey times on the key East Anglia route.
The A47/A11 Thickthorn junction scheme will also support development of 44,000 new homes in the area.
Enabling works are already underway, with main construction due to complete by 2028/29.