Motorists are being urged to take extreme care on the roads this afternoon because of icy conditions.
Roads in the northwest and northeast were worst affected this morning.
Meanwhile, severe weather conditions have been forecast for parts of Connacht and Ulster later tonight.
Met Éireann has issued a storm warning for Connacht and Ulster tonight, with winds expected to reach up to 140km/h.
AA Roadwatch says that icy conditions affected parts of Leinster and Ulster.
There wasl black ice on the M1 between Dunleer and Castlebellingham, although conditions along other parts of the motorway have improved.
There were several collisions along the route this morning.
Conditions were dangerous in several areas - including Kilkenny city, on secondary routes in Co Kildare and in Co Louth around Ardee.
In Donegal, driving conditions in the Barnesmore Gap, Meenaroy and Binbane areas are still poor.
P&O Ferries has announced that tomorrow's 4am Larne to Cairnryan sailings have been cancelled, due to forecasted adverse weather conditions.
Passengers will be accommodated on the 11.59pm sailing tonight or the 7.30am sailing tomorrow.