Road conditions in the northwest improved greatly during the day following overnight freezing temperatures and snowfalls.
However, motorists have been advised to take extreme care on back roads and sheltered spots in Co Donegal.
Roads in Co Wicklow have also been badly affected. The 44B is out of service until further notice, while the 44 is running to Kilternan but not to Enniskerry.
DART services in Dublin have returned to normal.
Some ferry services have also been affected. Irish Ferries says the Swift sailings from Dublin to Holyhead have been cancelled. Passengers will be accommodated on Cruise sailings instead.
The cold spell is expected to continue with Met Éireann forecasting temperatures as low as –3 Celsius in places tonight.
