Opposition politicians have asked Minister for Transport Martin Cullen to "justify the €1 billion cost of Dublin Port Tunnel" and show how it can be used by more than the current level of 12,500 vehicles a day.
Fine Gael and Labour have also called for the minister to review plans for a single point toll on the M50, claiming the €113 million cost and three year development period is too long and too costly.
Addressing the Oireachtas Committee on Transport last week, Fine Gael spokeswoman for transport Olivia Mitchell said Dublin Port claimed to be operating at capacity and she asked where any additional truck traffic would come from, if lorry numbers were to rise.
She asked Mr Cullen how the cost of the tunnel could be justified in view of the fact that Dublin Port claimed to be operating at capacity and there was no prospect of the numbers of lorries coming off ships increasing significantly. She added that the figure of 12,500 vehicles only included about 6,500 lorries in any case.
It was, she said, a poor investment of "about a billion" for such low volumes of traffic in a tunnel that can handle the same traffic volume as the M50, which is in excess of 100,000 vehicles a day at times.
She told the committee that "not one" bus currently uses the tunnel. Speaking later to The Irish Timesshe pointed to traffic congestion in north Dublin as ample evidence that some buses should be routed from the area between Santry and Swords, through the tunnel in peak times, when the tunnel is otherwise empty.
"I am not saying use it to bring more cars into the city, but it would take a lot of traffic out of the north city if it was a busway operating like a Luas," she insisted.
Labour's Transport Spokeswoman Roisin Shortall was also sharply critical and both women questioned the long lead-in time to develop barrier-free tolling and asked the Minister if he had not considered any different way of raising the money.
However Mr Cullen said he believed the €113 million operation "would provide value for money".
Under the proposed arrangements he said the current operator, NTR, would "be taken off the pitch from next year".
Once in the Government's hands the extra revenue would be "ring fenced" for road building schemes in the rest of the State, he promised.
