A 72-kilometre new road between Limerick and Castletown, Co Laois, will form part of the National Roads Authority's plan to reduce travelling times to the capital by half an hour.
The preferred route, which is subject to An Bord Pleanβla approval, will incorporate the existing Nenagh bypass which is to be upgraded to a dual carriageway.
The plans include the construction of a £154 million motorway between Limerick and Nenagh, covering 37 km. The remainder of the route will go through north Tipperary into Offaly and connect with the Castletown to Portlaoise M7 scheme.
The combined cost of the projects unveiled yesterday amount to about £370 million and cover a third of the 200-km long Dublin-Limerick road.
The cost includes estimates for compulsory purchase orders and compensation payments to landowners.
Other National Road Authority projects on the route include the Kildare bypass and the Monasterevin bypass, and the upgrading of the Naas dual carriageway and the Portlaoise-Cullahill road which will also be tolled.
Depending on the successful granting of planning permission, the projects are expected to be completed by 2006. The projects are expected to lead to a half-hour reduction in the average 2 1/2-hour driving time on the 200-km road despite a projected doubling in traffic by 2025.
Mr Kerry O'Sullivan, of MC O'Sullivan consultants, said daily traffic passing Nenagh would increase from 10,000 vehicles a day to 19,000 in 24 years.
About 200 landowners will be paid compensation but this will depend on a successful conclusion to talks between the IFA and the Government over compensation levels.
Opposition groups, however, are expected to put up stiff resistance when the two projects are referred to An Bord Pleanβla for approval.
Mr Barry Gleeson, of the Nenagh-Limerick Community Steering Group, said single lane carriageways could achieve the level of service the Government is seeking.