Unions at Irish Rail are warning of a winter of discontent if agreement cannot be reached over a pay claim.
Talks get underway at the Workplace Relations Commission (WRC) on Monday, after being returned there by the Labour Court earlier in the summer.
The company says it is carrying major debts and cannot afford an increase.
Unions want an extra 3.75% but the transport company has told the Labour Court it is in a 'perilous financial situation', and may need to cut four routes to stay afloat.
Routes in the firing line include Limerick to Ballybrophy and Limerick Junction to Waterford.
Irish Rail say axing them would save around €5m a year.
The National Bus and Rail Union (NBRU) says they are simply asking management to pass on pay hikes in line with others in the transport sector.
Its general-secretary is Dermot O'Leary.
"We're hoping the company will come to the table at least with some offer - and unfortunately if they don't then we see a situation where, certainly heading into the autumn, you could have a situation where there'd be strike on our railways.
"The best thing we can all do to avoid that is sit down and have sensible conversations.
"But if it doesn't happen, and the company continue with the line of the poor mouth, then unfortunately we are heading into a situation where there will be industrial unrest in the railway".