The M50 is facing "intolerable congestion" unless multi-point tolling is introduced, Transport Infrastructrue Ireland has warned.
Speaking before the Joint Committee on Transport, Tourism and Sport, TII Chief Executive Michael Nolan said traffic on the M50 has grown by 30% since 2012 and current measures to reduce congestion simply "sweat the asset" rather than improve capacity.
Mr Nolan said these included improving response times for incidents on the motorway to 13 minutes, improved markings to reduce the impact of merging traffic and signposts for diversion routes.
He said the TII is also awaiting a change in the law to allow the introduction of variable speed limits by next year which will mean smoother traffic flow and the reduction of rear-end collisions.
However, Mr Nolan added that "the level of traffic growth will ultimately result in an intolerable level of congestion and economic loss and the failure of the motorway to adequately fulfil its strategic functions. Without demand management in the form of multi-point tolling, M50 customers will continue to pay in terms of lost time and productivity."
He said the decision on multi-point tolling is a matter for Government and not one the TII is currently pursuing.
Fianna Fáil spokesman John Lahart for Dublin said the TII should "forget about multi tolling".
"It would have catastrophic effect on residential traffic. There’s no public appetite for it, there's no political appetite for it".
Green party leader Eamonn Ryan TD said he attended the An Bord Pleanála hearing on widening the M50 and said it was a "mathematical certainty" that there would be gridlock.
He said building super highways for cyclists would reduce congestion on the motorway but the budget for cycling infrastructure is collapsing, while the TII is planning to widen approach roads on the N7, N2, N3, N4 and N11 "into a city that cannot cope".
Mr Nolan said the TII had a statutory remit to ensure safety on the national road network.
He said the congestion on the M50 had resulted from a time lag in investment in public transport and he agreed that "we can't keep building beyond the M50".