Tolls or traffic lights may have to be installed at entrances to the M50 within a few years to curb traffic use of the motorway - despite a massive upgrading planned over the coming years.
The Joint Oireachtas committee on Transport heard yesterday that the €750 million upgrade programme would involve the construction of a third lane and new interchanges.
However the chief executive of the National Roads Authority, Mr Michael Tobin, said that within a relatively short period of time, traffic volumes on the M50 would again reach or go above capacity levels.
He said that this upgrade was "the last roll of the dice" for the M50 and that the State would not be able to increase capacity further. He suggested that when capacity on the motorway had been reached, "traffic management measures" would have to be considered.
This could involve restricting traffic on approach roads to the M50, he said, by way of traffic lights at the motorway's entrances.
Mr Tobin also indicated that tolls on approach roads "were a possibility".
He said that the NRA had looked tentatively at a further orbital motorway beyond the M50 "which may or may not include a new road over the Wicklow mountains".
NRA sources said it was provisionally looking at a route from Drogheda to Naas through Navan.
Mr Tobin also revealed that the board of the Authority had asked the executive to look again at the controversial eastern bypass motorway under Dublin Bay.
He said that this had been put on a shelf about two years ago as it had a price tag of around €1.5 billion and presented a number of environmental difficulties, such as Sandymount strand and the marshes at Booterstown.
