The Leinster Outer Orbital or Dublin Outer Orbital Road was a long motorway bypass proposed for Dublin. Its primary purpose is to relieve the M50 of the duty of carrying long distance traffic, leaving it as a distributor road for the city.
This long motorway was initially described as being around 100 km long, then 80km. Based on rough alignments identified so far, its length would be closer to 74 km. It did not have funding under the Transport21 plan, so only route selection and other basic work could take place on it up to 2015. However, the government had repeatedly reaffirmed that this motorway was a priority and would be undertaken after 2010 when the interurbans were finished.
In the 2010s, the road was estimated to cost €2B and would be tolled.
Note the the road does not have a confirmed number yet. The road is most commonly known as the Leinster Outer Orbital, previously the Dublin Outer Orbital Road (DOOR). Its number was previously predicted on this site to be 40 but in February 2012 this number was assigned to the Cork Southern Ring Road. Therefore, M45 is a more likely candidate, being numerically close to M50, a road which performs a similar function.
Like the M50, the M45 is a new build road and does not replace an existing route. There is no N45 at present, just as there has never been an N50.
New roads in the hinterland of a major city always attract new commercial and industrial development. Sure enough, in 2008 it seemed that the lands abutting the corridor were already in demand.
Update Nov 2015:
Recently a draft Transport Strategy for the Greater Dublin Area 2016-2035 was released.
It confirms that up to the horizon year of the plan, no work will take place on this road, though its route will be kept clear of development for possible later implementation.
Update 09/11/2021:
The Government has published its transport investment plan for the next two decades.
Most projects will be public transport and active travel.
The Leinster Outer Orbital has been cancelled outright.
With changing priorities regarding road versus rail investment, it now seems unlikely to ever proceed.
