The National Roads Authority has called on the Government to provide €2bn for the completion of major urban routes by 2008.
The authority has suggested additional tolls as one way to raise the funds.
The NRA expressed frustration at what it says is the outdated legislation governing national monuments which has caused the situation.
It has called for archaeology to be more closely integrated into the development consent and planning process.
It predicted motorists could use the entire M50 motorway round Dublin by December, apart from 2.5km round Carrickmines Castle.
The authority confirmed that pilot schemes for the 2-plus-1-road type will go ahead in Cork, Leitrim, Monaghan and Donegal.
The road type is designed to reduce the risk of head on collisions, and the authority estimates it will reduce road deaths by 50 people per year.
