Motorists travelling between Cork, Limerick and Dublin will have to slow to 40 m.p.h. leaving and approaching the capital as work begins on an extra lane system on the N7 Naas dual-carriageway.
Further road works and traffic disruption will also affect the motorway network in west Dublin, and will continue for the next five years.
The works, to install a third lane and rebuild interchanges on sections of the N7 and M50 roads, will cost about €1.1 billion, and will be carried out in phases between now and 2009.
Broken into a number of overlapping schemes, the works will see temporary speed limits of 40 m.p.h. and traffic restrictions implemented on a phased basis.
Work begins tomorrow on the widening of the N7 Naas dual-carriageway to provide three lanes in each direction between Rathcoole and Naas. New flyovers will be built at Johnstown, Kill, Castlewarden and Steelstown.
The project will also encompass two new pedestrian bridges and a new local road linking Castlewarden to Kill, Johnstown and Naas. The cost of the project is €230 million, and it is due for completion in the summer of 2006.
Before that project finishes, however. the National Roads Authority (NRA) expects to have started work on phase one of the widening of the M50 motorway, between the N7 Red Cow interchange and the N4 interchange adjacent to the West Link.
Phase one of the M50 scheme is expected to start in September this year, and will, according to the NRA, continue for about 3½ years. The overlap between the N7 project and phase one of the M50 scheme is about one year, during which motorists can expect delays between the West Link N4 interchange and Naas.
In a "knock-on" effect, before phase one of the M50 three-lane scheme is complete, the NRA expects to have begun work - probably in late 2006 - on the widening of the northern section of the M50 between the Dublin Airport interchange with the M1 and the N4 interchange.
The southern section of the M50 between the N7 interchange and Sandyford in Dublin is also due to be upgraded to three lanes in each direction at the same time.
While the NRA said yesterday the timescale priority for these sections of the M50 has yet to be announced, the Dublin Port Tunnel would open in mid-2006, linking the northern M50 with Dublin Port.
The NRA said it would be putting a traffic management plan in place to manage the M50 road schemes. A spokeswoman acknowledged that these schemes would take about five years.
While the traffic management plan will aim to keep two lanes of the M50 open in each direction at all times, temporary speed limits of 40 m.p.h. - changing to 60 k.p.h. when the system goes metric this month - will be in place, and some lanes will be narrowed on a temporary basis.
There are three major upgrades designed for "almost" free-flow interchanges. They are at the M1/M50 junction; the N4/M50 junction and the N7/ M50 junction.
There will also be less extensive upgrades of eight interchanges at Sandyford; Ballinteer; Scholarstown; the N81/M50 junction; Ballymount; Blanchardstown; the Ashbourne/M50 junction and Ballymun.
