Up to 2,000 people will be affected by further industrial action today as train drivers stage an unofficial strike in Counties Mayo and Roscommon.
No trains will operate in or out of six stations on the main route to Dublin.
Six drivers have placed pickets at Westport station in a protest over pay and rostering arrangements.
They claim to be the only drivers in the country who have not received an award approved in 2001.
Iarnród Éireann said the action was totally unjustified as the dispute is due before the Labour Court later this week.
The action follows disruptions to Dublin bus services yesterday when more than 500 drivers attended a union meeting.
They were protesting at Minister of Transport Mr Seamus Brennan's plans to privatise around a quarter of the city's bus routes later this year.
SIPTU and the National Bus and Rail union are due to meet the minister on Monday.
CIE are also expected to demand a "jobs for life" promise similar to that given to Aer Rianta staff two weeks ago by Mr Brennan in a bid to avoid strikes at three airports.