Dublin Bus has said it will begin to implement an €11m cost cutting plan without delay, after a ballot of drivers resulted in 55% voting in favour of the cost-reduction measures.
However, the ballot has split the drivers’ unions, with the National Bus and Rail Union passing the plan and SIPTU rejecting it.
SIPTU drivers voted to reject the measures by a margin of 51% to 49%.
NBRU drivers accepted the proposals by a margin of 60% to 40%.
Responding to the ballots, Dublin Bus said: "Given that 55% of drivers have accepted the proposals of the expert group and all other grades have accepted the Labour Court Recommendation, Dublin Bus will now commence with the full implementation of the Cost Recovery Plan for all grades without delay.
"An implementation date will be announced shortly."
SIPTU said it had not received "adequate assurances" from the firm about the future of the public bus system.
Organiser John Murphy said: "It is clear from today's result that SIPTU Dublin Bus drivers are of the opinion that they cannot endure any further cuts to their earnings."
Mr Murphy said the union is willing to meet management for further talks on the dispute.
Dermot O'Leary of the NBRU said there had been a constant unfair focus on drivers’ terms and condition due to a financial crisis not of their making.
Minister for Transport Leo Varadkar and Minister of State for Public Transport Alan Kelly have noted the result of the ballots.
They expressed deep concern at the outcome of the SIPTU vote.
Both ministers said they were calling on SIPTU to join with all other grades in accepting the overall outcome of the vote and the views of the staff as a whole, as any strike would be prolonged.
They added that it was hard to see how any such strike could be resolved.
Both Mr Varadkar and the company had warned that the outlook for Dublin Bus and its employees was "stark" if drivers failed to accept the latest proposals.
In a statement last week, Mr Varadkar warned that if the proposals were rejected, there was no realistic alternative.
In July 2012, the Cabinet was forced to approve a €36m bailout for CIE, which was conditional on the implementation of cost reductions by August that year and the sale of certain assets.
However, 15 months on, although all grades other than the drivers have accepted the cuts, no savings have been secured.
Two days ago, the National Transport Authority announced that CIE fares, including at Dublin Bus, are to rise from next month, with the remainder to increase in December.
NTA Chief Executive Gerry Murphy said cost-reduction programmes had been put in place by the operators, but these had taken time to implement, and costs had not fallen to the same extent as the State subsidy and revenue base.
The latest proposals at Dublin Bus were formulated by industrial relations experts Noel Dowling and Ultan Courtney.
Their report outlined some of the "difficult options" being considered if the proposals are rejected.
The investigators noted that if a strike happens, it will be prolonged and very difficult to end given that all processes have been exhausted.
They said that in that event, there will be no winners, and all sides will be worse off.