SIPTU train drivers at Irish Rail have voted overwhelmingly in favour of industrial action.
92% of drivers voted for the action as the dispute over productivity continues. The ballot was counted this morning in Dublin's Liberty Hall.
The union says the company has reneged on a commitment to discuss past productivity and if they do not honour the terms of that agreement, it will inevitably lead to disruption of services.
SIPTU organiser Paul Cullen said: "The result of this ballot, which saw 92% of drivers vote in favour of industrial action, indicates the level of frustration felt at the company's refusal to honour an agreement it entered into in September 2014.
"Our members still hope that management will step back from the brink and honour the terms of this agreement to negotiate on past productivity produced by drivers."
The union will meet on Thursday to decide what form the action will take.