An €810 million upgrading of the M50 motorway to include a third lane in each direction for 31 km has been approved by An Bord Pleanála.
Widening the motorway and upgrading 10 of the access points along the route is intended to reduce the average travel time by 19 per cent in 2008 and 11 per cent in 2023.
The upgrade covers the distance between the M1 and Sandyford, with the provision of auxiliary weaving lanes between the M1 and Scholarstown generally within the existing motorway boundaries.
The upgrading includes modifications to 10 interchanges to provide full or partial free-flow for the principal turning movements. The Westlink toll plaza will be upgraded to a fully electronic free-flow facility.
The application was made by Dún Laoghaire-Rathdown County Council.
An Bord Pleanála in its decision concluded that, subject to some modifications, the proposed road development "would not give rise to significant adverse effects on the environment or be contrary to the proper planning and sustainable development of the area".
Among the adjustments called for by the planning board was that the design of the Ballymun interchange be modified at the the Naul Road approach, to facilitate the future development of a quality bus corridor on the road and the future development of lands adjoining it.
Many of the plans for the sections have also been slightly modified to reduce the impact on adjoining properties.
To protect the residential amenities of the King's Hospital School at Palmerstown and to limit the field of vision for users of the overbridge of the school's facilities, the height of barriers must be increased to 3 metres and screening provided along the ramp to the bridge.
The planning board also decided that local liaison committees should be established by Dún Laoghaire-Rathdown County Council at the detail design stage of the scheme for several of the interchanges to provide information for local community, business and commercial interests likely to be affected by the construction work.
The first phase of the upgrade between the N7 at Naas Road and the M4 at Lucan Road is expected to start early next year. The whole project will take four years.
Minister for Transport Martin Cullen said yesterday: "The M50 upgrade is a vital part of the Government's roads programme. Whilst the upgrade won't solve all traffic problems on the M50, it will bring benefits to road users. The addition of an additional lane means the M50 can better cater for traffic. Equally, modification of the interchanges will improve traffic flows."
He said the Government had asked the National Roads Authority (NRA) to carry out a feasibility study for an outer ring road of Dublin.
"Infrastructure must be planned well and planned early. An outer ring road will not happen overnight, but now is the time to explore how it could work, the difference it could make and how much it would cost.
"On transport infrastructure, we have a responsibility to think about the future and that is what the Government is committed to," the Minister said.
However, Green Party TD Paul Gogarty said the decision to widen the M50 would consign 100,000 west Dublin commuters in Clondalkin, Lucan and Palmerstown to four years of unprecedented traffic gridlock.
"Unless the Government takes action to provide a rail-based alternative, the area will become one big traffic island," he said.