The multimillion-pound upgrade of the Westlink in Belfast took a major step forward when the Broadway Underpass opened today 13 months ahead of schedule.
A big easing of congestion for thousands of commuters is expected, as well as a cut in the time it takes to make the link between the M1 motorway and the M2 and M3 on the other side of the city.
Two lanes in each direction are open through the underpass and this will rise to three when further above-ground work is completed in the coming months.
The entire £104m (€131m) Westlink scheme, which started in January 2006, is due for completion ahead of schedule next year.
The scheme will improve access to the George Best Belfast City Airport and Port of Belfast, something the freight transport industry has been pressing for years.
Roads Minister Conor Murphy welcomed the opening of the underpass.
He said: “The transfer of traffic to Broadway underpass is the most significant milestone to date in the upgrade of the M1/Westlink.
“Mainline traffic should see an immediate improvement as vehicles will now be able to travel uninterrupted along the M1 and Westlink.
“With two-thirds of the traffic now using the underpass, this will improve access across Broadway for pedestrians and will provide the opportunity to improve access to the Royal Group of hospitals.”