Passengers are bracing themselves for travel chaos when Bus Eireann drivers go on strike on Sunday.
The company said it hopes to operate as many services as possible, despite workers with the National Bus and Rail Union (NBRU) staging the walk out from midnight.
Bus Eireann revealed it was difficult to plan ahead as the company did not know if members of Siptu, who are also being balloted for industrial action, would pass the picket.
Approximately 50,000 customers usually travel on routes across the country on a Sunday.
A spokesman for the company said: "We will endeavour to operate as many services as possible as long as it is safe to do so, however this will depend on the level of strike action taken. Customers are advised to visit buseireann.ie and local and national media for updates."
The strike, which centres on a row over payroll savings of five million euro, is expected to cost Bus Eireann 200,000 euro a day. Both sides have said they are available for talks but no contact has been made so far.
Michael Faherty, NBRU general secretary, claimed the company had selected the date for the walkout as it is the day the firm wanted to implement new measures which he described as a breach of contract of employment.
He said: "I have nothing but sympathy for the travelling public, they haven't caused this. The management should be thinking about their customers too and should be sitting down with trade unions to negotiate."
Translink has already confirmed that several cross border Ulsterbus Goldline coach services will be affected until further notice, with only buses driven by Translink drivers running at reduced frequency.
"As the Bus Aras depot in Dublin will not be available as a drop off /pick up point in Dublin city centre, an alternative temporary stop will be located at Custom House Quay," a spokeswoman added.