The opening of the final leg of Dublin's C-ring motorway on Thursday will put in place an "east coast motorway spine" from Rathnew in mid-Co Wicklow to Dundalk, Co Louth, a distance of 155km (96 miles).
The opening will also see transport planning in Dublin moving away from roads and into "a new phase of public transport provision", according to the National Roads Authority (NRA).
As well as delivering the east-coast motorway spine, the completion of the M50 will also link Wicklow to south of Portlaoise, Co Laois, via motorway or dual-carriageway. Locally, the South Eastern Motorway will greatly improve access to Dublin from north Co Wicklow and the southeast.
Crucially, traffic heading north along the N11 will no longer have to pause for the Loughlinstown roundabout or negotiate suburban traffic between the Loughlinstown and Leopardstown roads.
Access from the Sandyford Industrial Estate to the M50 - and so the rest of the major roads network to the regions - will also be greatly improved.
Improved access to the Cherrywood lands will also speed up the residential and commercial development there.
Three new interchanges will open immediately, with the Carrickmines interchange due to open by October. The interchanges which open immediately are the Dundrum/Sandyford junction at Murphystown, the Cherrywood junction and the junction with the N11 at Shankill.
The most complex is the Dundrum/Sandyford junction, through which 14 lanes of traffic will be passing. Large overhead gantries have been put in place to advise motorists which lanes should be taken for access to Dún Laoghaire port, Leopardstown racecourse, south Dublin, the industrial estate, and the N11 for Wexford.
According to the NRA, the completion this year of the Dublin Port Tunnel means the only project the NRA is then committed to starting in the Dublin area is the upgrade of existing elements of the M50.
The corporate affairs director of the authority, Michael Egan, said public transport would play a dominant role in new infrastructure.
"We are signed up to the Dublin Transportation Office Platform for Change, which sees the solution to transport as an integrated solution of which we are only a part," said Mr Egan.
"Public transport has a big role to play, and I think you will see future developments in Dublin are in that area. We have never said investment in roads will solve all our problems - it can't."
While the authority is commissioning a feasibility study into an outer bypass of Dublin along a route close to Drogheda, Navan, Trim and Naas, there are no State commitments to it. Nor is there a commitment to an eastern bypass of Dublin city.
