Overnight frost has resulted in black ice forming on major routes in many areas, with the AA advising drivers to take extra care.
It reports the M11/N11 Dublin/ Wexford Rd is closed both ways between Brittas Bay and J20 Arklow North, while extreme care is advised south of New Ross between Newbawn and Foulkesmills in Co Wexford.
There are reports of icy conditions around Roscommon town, in the Ballymote/Boyle Rd in Co Sligo and on the N10 Kilkenny/ Knocktopher Rd in Co Kilkenny.
There are further reports of black ice in Carrick on Shannon, Manorhamilton and Drumshanbo in Co Leitrim.
Meanwhile, a jack-knifed truck on the Ballinasloe/ Kilconnell Rd in Co Galway has been cleared and in Cork, care is being advised on secondary roads.
Met Éireann earlier issued a status yellow weather warning for snow and ice for Connacht and Ulster.
The warning lasted until 10am on Wednesday and the weather service predicts some wintry showers and possible snow on higher ground in the affected areas.
It forecasts an otherwise bright and cold day.
Western counties will see scattered heavy showers, while eastern counties should remain dry. Highest temperatures are expected to be between four and six degrees Celsius.
Tonight is predicted to remain mainly dry and clear but chilly again, with lower temperatures between zero and minus three degrees.