As freezing temperatures persist across Northern Ireland, representatives for the region's roads service have revealed that gritting the main network is costing £150,000 a night – twice as much as normal on account of the need for "double salting".

While Northern Ireland car insurance customers take all the advice they are offered to ward off a potentially fatal accident, air travel continues to be disrupted and a number of rural schools have been closed.

To keep over 4,000 miles of roads open and safe for traffic, the roads service has had up to 134 gritting lorries in action overnight, though drivers are still urged to exercise extreme caution, particularly if they hit an untreated road.

Temperatures in Northern Ireland dropped as low as -5C this week, with the north-west of the region particularly badly hit. Derry's Altnagelvin Hospital has now treated more than 100 people who needed surgery after slipping on ice over the past two weeks, while accident and emergency departments in Belfast's Royal Victoria Hospital and the Ulster Hospital in Dundonald have also been dealing with increased patient numbers.

Motorists in Northern Ireland have been warned to expect the freezing conditions to persist for another ten days.