The N11 southbound has reopened in Co Wicklow following a collision.
The road had been closed earlier this afternoon at the Bray South exit (Southern Cross).
A cyclist has been seriously injured after being in collision with a car.
Traffic is still very busy and gardaí are advising motorists to avoid the area.
This morning, drivers were advised to exercise caution on the roads due to hazardous weather conditions.
Met Éireann said that temperatures dropped to as low as -8C in the Cavan/Monaghan area overnight.
It expects the cold snap to last for the next two days.
However, AA Roadwatch reported that while it remains extremely cold nationwide, it appears to be a dry frost and it has had no reports of severe or black ice.
Road temperatures remain below -0C on roads in counties Monaghan, Cavan, Westmeath, Longford, Leitrim, Limerick and Roscommon.
Gardaí are advising motorists to avoid the Sally Gap in Co Wicklow due to icy conditions.
