Met Éireann issued an orange status weather alert for the second day in a row as heavy frost and fog followed freezing temperatures overnight.
The alert is in place for counties Cavan, Monaghan, Donegal, Dublin, Kildare, Longford, Louth, Westmeath, Meath, Leitrim and Roscommon and is active until 9am.
AA Roadwatch is reporting dense fog on the M1 between J7 Julianstown and J10 Drogheda North.
It also advised that motorists take extra care and use fog lights in affected areas.
From today, An Garda Síochána can take blood samples from any driver involved in a crash who has been incapacitated through injury and is unable to give explicit consent.
Under the new regulations, medical personnel will take the samples. Upon regaining capacity the injured party will be asked if they consent to the issuing of a certificate of the test results.
This certificate can be used in later legal proceedings and a refusal to allow for it to be used will be viewed in the same way that the refusal to provide a sample to gardaí is an offence.
Gardaí will also have greater powers to conduct roadside testing for driver impairment due to the use of drugs.
The new test will include cognitive tests including touching the nose and walking in a straight line.
Minister for Transport Pascal Donohoe will announce the closure of a loophole at the launch of the annual Christmas road safety campaign.
As of Wednesday morning 179 people had lost their lives on the country’s roads, 18 of which died in November alone. Of the total, 35 were pedestrians, 76 were drivers, 36 were passengers, 20 were motorcyclists while 11 were on pushbikes.