Bus and train services in the six counties are facing disruption o due to strike action over pay by three trade unions, Unite, GMB and Siptu.
It follows two days of strike action last week, which led to no public bus or train services. Previous strikes took place on 1 December and 15-16 December.
Normal timetables will resume on Saturday 23 December.
A limited Dublin-Belfast service is operating.
Representatives from all three unions said they will be meeting early in the new year to discuss and identify further strike dates.
