The major new £162M A5 to M1 link road and junction in Bedfordshire is now open to traffic.
The new 4.5km long dual carriageway will now become part of the A5.
Also opening is the new M1 junction 11A which connects the new dual carriageway and another new link road built by Central Bedfordshire Council, to the M1.
A Costain and Carillion joint venture started construction in March 2015 which has included the building of two other new junctions and six new bridges.
The new road replaces a section of the A5 through Dunstable which is being handed over to Central Bedfordshire Council and Hertfordshire County Council.
However Highways England said some minor work including the completion of new sign installation would need to take place after the new road is opened and the old section handed over to the council.