Disruption to rail services in south Dublin, Wicklow and Wexford are expected to continue all week.
It is after signalling equipment was damaged in a fire at the weekend.
Passengers travelling between Rosslare and Dublin will be transferred by bus from Greystones.
Irish Rail's Barry Kenny says there will be reduced services between Bray and Dalkey, and none between Bray and Greystones.
"We had a major incident on Friday evening in which a signalling equipment room suffered fire damage," said Mr Kenny.
"There is a lot of cabling that controls the signalling between Dalkey and Greystones.
"Throughout this week we will have no services between Greystones and Bray. We will this morning be having some shuttle bus services between Greystones and Bray.
- Digital Desk