The Big Freeze is set to continue for another week with "treacherous" driving conditions as temperatures dip to as low as -10C at night, weather experts warned.
The longest cold spell since 1963 in Ireland meant that road temperatures remained below zero in many areas as hundreds of thousands of commuters went to work today.
It also also emerged that councils were told in November by the Department of Transport to buy grit to prepare for the extreme weather.
Some local authorities have run out of supplies and 14,500 tonnes of salt and grit are being imported this week in a bid to redress the shortage.
National routes were gritted and passable today, although there were reports of ice in midland counties, while driving on secondary roads was still dangerous from snow and ice.
Road conditions remained poor in many parts, especially the N4 Dublin/Sligo road at Sligo, the N3 Dublin/Cavan Road at Cavan town and the Lee Road in Cork.
In Dublin, there were “extremely icy” conditions on the Skerries/Lusk Road and on the Lusk/Rush Road, while the Phoenix Park, the Chapelizod, Islandbridge and Knockmaroon Gates will stay closed until tomorrow due to icy conditions, AA Roadwatch said.
Traffic on the M50 was moving well at rush hour this morning but some roads in Howth were extremely icy, including Carrickbrack Road, Windgate Road and Wingate Rise.
Although local authorities were told last November that money was available through a Department of Transport discretionary fund, thousands of kilometres of local and regional roads remain hazardous because grit has not been laid.
South Dublin Co Council said the level of activity was “stretching the council’s resources” and that gritting was dependent on more being sourced.
Many local authorities are short of rocksalt needed to keep roads free of ice. Roads affected include former national routes which still carry large volumes of traffic.
An average of 45,000-55,000 tonnes of salt is typically used for gritting roads during the winter period from October to April, but more than this amount was used between October to December because of the freezing temperatures.
The first shipment of 4,000 tonnes arrived in Cork yesterday from Spain and further supplies are scheduled to arrive in Limerick and Dublin over the next 72 hours.
Dublin Bus said it was operating a full service today, although there are still “curtailments” in some areas due to the weather conditions.
Bus Eireann said the majority of its services were operating as normal with some delays but advised customers travelling to and from Leinster and Limerick to contact their local traffic office for information on individual services.
The AA said it experienced its busiest day ever yesterday with more than 700 calls for help received by lunchtime.
Met Eireann said the cold snap is set to continue for another week with extremely cold, but mainly dry, weather continuing through the rest of the week and over next weekend across the whole country.