A status yellow fog warning has been issued for the entire country.

Met Éireann is forecasting dense fog in many areas. The alert is in place until 10.00am on Saturday.

It comes as thousands of people take to the roads for the Christmas break.

The Road Safety Authority (RSA) and ESB Networks are calling on people to wear high visibility clothing, carry torches and take appropriate precautions when using the roads.

The advice has been issued ahead of 'National Be Safe, Be Seen Day' on Sunday - the shortest day of the year.

It aims to remind people of the importance of wearing high visibility material when out walking, cycling or motorcycling.

A status yellow fog warning | Image: Met Éireann

It also encourages the public to do so throughout the year, but especially on the shortest day of the year and during the darkest months of the year.

The RSA says some 60% of fatal pedestrian collisions happen in hours of darkness.

To date this year, 141 people have died on Irish roads compared to 135 this time last year.

Vulnerable road users - such as cyclists, motorcyclists and pedestrians - accounted for 50 deaths; 26 pedestrians, 16 motorcyclists and eight cyclists.

Speed is a factor in one-third of fatal crashes, and research shows that the speed a car is travelling at has a marked impact on survival rates.

A pedestrian hit by a car at 50km/h only has a 50% chance of survival; hit at 30km/h a pedestrian has a 90% chance of survival.