The travel plans of up to 100,000 rail users, including 55,000 Dart customers, will be ground to a halt by today's Irish Rail strike.
The 48-hour stoppage, which began yesterday in response to unilateral wage cuts, will cost businesses in Dublin tens of millions of euro, it is estimated.
And there was no sign last night of a breakthrough that could prevent further walkouts - planned for September 7, 8 and 21 - from going ahead.
It is now feared an all-out strike will be staged if the cuts are not reversed.
Iarnrod Eireann said there has been no fresh contacts between management and trade union representatives.
"There are none scheduled. We have had 20 months of talks. We had the measures [pay cuts] implemented today. They are essential. We are available for talks on any other issues of concern," the semi-state's spokesman Barry Kenny told the Herald.
"In terms of the pay cuts, they have to go ahead to protect employment and protect the company," he added.
Iarnrod Eireann would be insolvent by the middle of next year without the reductions, he said.
SIPTU and the National Bus and Rail Union (NBRU) are staging a combined five days of industrial action, with yesterday's stoppage hitting 60,000 rail customers including thousands of GAA fans attending Croke Park for the All-Ireland football semi-final between Kerry and Mayo.
The upcoming strikes will affect the All-Ireland hurling final on September 7 and the football decider on September 21.
NBRU general secretary Dermot O'Leary said a "broader issue is at play" in the dispute, adding that Transport Minister Paschal Donohoe has a responsibility.
"The [State] subvention has gone to 1998 levels. The minister has a central role to play here. He needs to address the underlying issue. [Iarnrod Eireann] is asking people to put their hands in their pockets and reduce their wages without any guarantees," he told the Herald.
"There are three stakeholders here: the company, the Government and the workers. There was an agreement in 2012 that was supposed to last four years. The company came back 11 months later and asked for wage cuts," he added.
Mr O'Leary believes that non- payroll expenditure worth more than €200m could have been reduced before workers' salaries needed to be cut.
"There is no railway in the world that makes money. Railways across Europe are increasing their subvention year on year. The Government needs to decide first if it wants a rail service for its citizens or not," he said.
But Mr Kenny called for "realism" among the leaders of the trade unions. "They are temporary and modest pay cuts about protecting ... the company and employment within it," he said.
The dispute revolves around pay cuts of between 1.7pc for those earning €56,000 and 6.1pc to workers on over €100,000 lasting for 28 months.
The strike will cost the rail company around €1.3m in customer revenues and public service payments.
Iarnrod Eireann chief executive David Franks cut short his holiday in Mauritius after it emerged he had not been due to return until today.
The dispute will cost Dublin city businesses more than €25m in lost revenue according to DublinTown, a representative body for over 2,500 firms.
Mr Donohoe has said he will not be getting involved in the row, but Fianna Fail transport spokesman Timmy Dooley called on the minister to have discussions with both sides.
Mr O'Leary said a review of the union's position is to take place in September. "We are having a review on September 23 and, as far as the NBRU is concerned, they have "a mandate for industrial action including all-out strike".
Dublin Bus and Luas services will run as normal today.
Commuters were advised to leave extra time for journeys due to increased passenger numbers.
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