A limited rail service has resumed on the Northern line following the cancellation of all services this morning due to a freight train derailment.
Thousands of commuters suffered severe disruption today after the train derailed south of Skerries last night. Some services will operate this weekend, but repairs are continuing on the lines.
All services between Dundalk/Drogheda and Dublin were suspended, and customers were forced to make alternative arrangements this morning.
Traffic was extremely heavy on the M1 due to the cancellation of the train services. Iarnród Éireann said a limited northbound service is operating this afternoon on the Dundalk/Drogheda and Dublin services.
It said "close to full" northbound services will operate at evening peak time. Southbound services will be limited.
On the Dublin-Belfast-Dublin route, the 13.20hrs Belfast Enterprise service was in operation and all subsequent services will operate with minor delays up to the 20.10hrs service from Belfast to Dublin.
That train will run to Drogheda with bus transfers from there to Connolly Station in Dublin.
After last services tonight, the Northern line will be closed and remain closed through the weekend to allow track repairs, Iarnród Éireann said. There will be no Dundalk/Drogheda and Dublin service on Saturday and Sunday.
On the Dublin/Belfast route, northbound Dublin/Belfast services will operate by bus transfers from Dublin Connolly to Drogheda and by rail from Drogheda to Belfast.
Southbound Belfast/Dublin services will operate by rail from Belfast to Drogheda and by bus transfer from Drogheda and Connolly.
Iarnród Éireann warned customers to expect a delay of 30 to 40 minutes on these services.
Dart services will operate as normal.
Bus Éireann provided transfers for some rail passengers earlier. Up to 7,000 people have been affected by the disruption.
The freight train, which was carrying mineral ore from Tara Mines to North Wall, derailed at Hackettstown at around 11pm last night. Six of the train's 11 wagons derailed, causing extensive damage to the tracks.
Irish Rail said it appeared the fault was with one of the 75-tonne wagons and not the rail track itself. "Our initial investigation would lead us to focus on to one of the wagon but we will investigate all factors," spokesman Barry Kenny said.
"This is certainly an extremely unusual and serious incident," he added.
Additional reporting: PA