A £6.5million overhaul of the A1 Black Cat roundabout is due to start in May.
The busy junction, which connects the A1 with the A421 to Bedford, is used by 52,000 vehicles a day and lengthy queues of traffic regularly build up at rush-hour.
A congestion-busting programme of work is planned, including:
n Enlarging the roundabout to create four lanes.
n Increasing the A1 northbound approach from two lanes to three.
n Increasing the A1 southbound approach from two lanes to four.
n Installing part-time traffic lights on the roundabout on both the north and southbound A1.
The Highways Agency is carrying out the work which is expected to take seven months to complete. It is part of the Government's £300m pinch point programme, set up to relieve congestion by making improvements to existing roads.