Work has started on improvements to a bottleneck junction and roundabout on the A45 in Northamptonshire.
The £5.3m project aims to cut congestion on Barnes Meadow roundabout on a busy route into Northampton.
New bus lanes, improved road safety and environmental benefits are promised by the county council.
"An important part of the scheme is to cut the journey time from Wellingborough and Earls Barton into Northampton," a council spokesman said.
Motorists will be hit by off-peak road and lane closures, temporary traffic lights and disruption over the six-week project term.
"We are asking all residents and businesses in the area for their patience, flexibility and co-operation in order to allow the scheme to progress efficiently," the spokesman said.
Project money has come from the Community Infrastructure Fund which supports transport costs in growth areas.
The Barnes Meadow roundabout, where the A45 and the A428 meet, is one of the busiest junctions in the county.
An average of 7,000 vehicles use the interchange during morning and evening rush-hours.