Dublin commuters are facing major disruption next month as Luas workers confirmed two 48-hour strikes.
Trade union Siptu has served notice of the industrial action on Transdev, which operates the tram, in a row over pay and conditions.
The first continuous work stoppage will take place on Thursday February 11 and Friday February 12.
Workers will also stage a walkout on Thursday February 18 and Friday February 19.
Owen Reidy, of Siptu, said union members are conscious of the inconvenience caused by the action but believe they have no other option.
"In talks over the last 18 months, Transdev has failed to offer an increase in pay for the next five years to Luas workers," he said.
"The company position in talks in all forums has been that it will only offer pay increases in line with the consumer price index (CPI).
"The CPI is currently, and has been for some time, a negative figure. This means that unlike 96% of other companies across the state Transdev is not prepared to pay any increase in pay in excess of that attached to workers' existing conditions of employment."
Mr Reidy also accused Transdev of trying to demonise Luas workers.
"Instead of attacking its employees, the management of Transdev would be better served considering why over 99% of Luas workers feel so frustrated that they voted for industrial action," he said.
"Siptu members hope that the company will reconsider its position and make a meaningful offer on pay."
Gerry Madden, Transdev's managing director, said the operator was disappointed with the strike action notice, and claimed workers' pay and conditions are "very favourable".
"The claims being pursued by Siptu on pay alone are between 8.5% and 53.8% depending on the pay scale, and would cost Transdev 30 million euro over the five years of the Luas operating contract - six million euro per year," he said.
"This is at a time when Transdev finds itself in a loss-making situation.
"The loss incurred by Transdev in 2015 was 700,000 euro and we are predicting further losses in 2016."
Mr Madden added that Transdev did not cut pay, freeze pay or change terms and conditions throughout the economic crisis.
"On the contrary Transdev increased pay between the years 2009 and 2015, with increments ranging between 1.25% and 5%. During this period we also reduced average working hours," he added.