A two-kilometre section of the M50 to Leopardstown is being officially opened today.
The motorway is expected to significantly affect the flow of through-traffic across south Co Dublin.
Traffic will have a direct route between the M50 and the N11 towards Wicklow and Wexford, and access will be facilitated between the M50 and Kilgobbin, Ballyogan, Murphystown and Leopardstown.
Previously southbound traffic on the M50 heading for Wicklow, Wexford and the southernmost parts of Co Dublin had to "double back" either through Marlay in Rathfarnham or through Sandyford Industrial Estate and access local roads to complete journeys.
However, the council will continue to advise traffic from Dún Laoghaire Port to leave the M50 at Ballinteer and access the port via the Ballinteer Road, Dundrum, the Wyckham bypass and Foster's Avenue.
The opening is also expected to dramatically reduce through traffic in the Sandyford Industrial Estate where a dedicated link to the Ballinteer interchange has become very congested. This route will remain open.
Today's opening does not include the new Sandyford interchange or a new link road to Kilgobbin. These areas will be accessible via Leopardstown Road.
The M50 is expected to be completed by August next year, pending a Supreme Court challenge to the work at Carrickmines Castle.