The National Bus and Rail Union have announced they are to seek a salary increase for rail workers, in line with what they describe as "industry norms".
The union has already lodged pay claims at both Bus Éireann and Dublin Bus.
They say their latest claim is justified due to a changing economy and increased passenger numbers at Irish Rail.
Luas workers are currently considering an offer by management to end their campaign of industrial action in pursuit of a wage hike.
There are reports their drivers have been offered pay increases of 18% over a period of just under three years.
The outcome of the Luas dispute is expected to be watched closely by other sectors in the transport industry.