Further salting of Northern Ireland roads today as snow and ice continue to cause difficult driving conditions

The Department for Infrastructure said the operation involved salting of the “entire scheduled network”.

Road users are advised to exercise caution when travelling, particularly when driving on untreated surfaces.

The Met Office says tonight (Friday) will be a dry evening with clear spells and a frost in places. However, cloud and outbreaks of rain will spread east overnight with a southerly breeze picking up and temperatures recovering. The minimum temperature is expected to be -1 °C.

Saturday is forecast to be a cloudy and misty day with occasional rain or drizzle. It will become milder with any lying snow gradually thawing. There will be fresh southerly winds, strong around exposed coasts. The maximum temperature is likely to be 6 °C.

Which roads are salted?

The Department for Infrastructure has outlined its criteria for salting how it focuses resources on roads carrying the most traffic.

A schedule of salting routes has been drawn up covering the main through routes carrying more than 1,500 vehicles per day. Other roads carrying more than 1,000 vehicles per day may also be included if they are in hilly areas or there are other difficult circumstances. Special allowance is made for school and other buses by a weighting factor. For example, a 40-seater bus is counted as 40 vehicles. Almost 7,000 km (4,300 miles) of roads are salted, which is 28 per cent of the length of the road and salting it costs £4.5m in an average winter. This caters for 80 per cent of all traffic. To cover 90 per cent of traffic, the length of roads salted would be doubled, at twice the cost. On more lightly trafficked roads, salt boxes or grit piles may be placed at hills, bends or junctions for use by the public.