Workers at Dublin Bus are to stage three 48-hour strikes next month in dispute over pay.
The strike action is due to take place on 8-9, 15-16 and 23-24 September.
The trade unions at Dublin Bus met yesterday and jointly agreed on the dates for the strike.
NBRU General Secretary Dermot O'Leary accused the company of playing "Russian Roulette with a public transport service that underpins the social and economic fabric" of the capital.
He said workers have not had a pay rise in eight years and also agreed to two-cost cutting plans "inclusive of pay cuts".
Dublin Bus workers are seeking a 15% pay increase plus 6% they say is owed since 2008 in order to bring them in line with pay that Luas drivers receive.
Mr O'Leary said the NBRU remains available for further talks on pay if Dublin Bus acknowledges that the Labour Court recommendation, which workers rejected six weeks ago, is "not adequate" to address the pay issue for all staff.
Mr O'Leary of the NBRU said that the Government needs to pay more to subsidise the bus service, saying that it had cut the subvention by €26m.
SIPTU Organiser John Murphy said: "Our members are calling on the management of Dublin Bus to immediately enter into discussions with SIPTU representatives to resolve this situation.
"However, at this point only a comprehensive agreement on all matters can avoid the commencement of a campaign of serious industrial action."
Dublin Bus said it is "extremely disappointed" at the announcement by the unions.
In a statement, the company said it had accepted the Labour Court recommendation, which provided for a cost of living pay rise of 2.75% per year for three years for each employee, which would see all grades receive a pay increase of 8.25% within a 16-month period.
The statement added: "Dublin Bus management will now arrange to meet with the joint Trade Union Group to outline the company's position, to discuss the issues in dispute and to seek a way forward to avert industrial action."
Speaking on RTÉ's Today with Sean O'Rourke, SIPTU Organiser Owen Reidy acknowledged that the strikes will cause chaos but said the union is open to talks.
He said that since 2014 the company has returned to profitability, largely due to the efforts of staff and while passengers numbers are up, pay is not.
He said workers are entitled to a share and they will not allow their pay to stagnate any longer.
"We have been involved in various sets of talks, local talks, the WRC and the Labour Court. I think what you are seeing now is a pent up frustration after eight years of pay stagnation."
He said SIPTU is seeking a 15% increase in pay over three years and some form of retrospective payment that was agreed and "promised back before the recession. It was agreed that it would be deferred to better times and better times have arrived."
Dublin business groups have condemned the planned strikes and claim it will have a devastating effect on the city's economy.
Patricia Callan of The Small Firms Association described the planned six days of strikes as "nonsensical" saying the Labour Court recommmendation of an 8% increase is far higher than most companies can afford.
The business group DublinTown estimates that six days of strikes will cost the city €15m.
A spokesperon for the Department of Transport would only say that it welcomes the announcement of talks by Dublin Bus.