Why can Northern Ireland roads refreeze after they have been gritted?

Roads can refreeze after gritting because salt does not work instantly or indefinitely, and fresh rain or showers can dilute or wash away the treatment.

Road-surface temperature can also fall again after spreading, particularly overnight or after a shower.

For “Why can Northern Ireland roads refreeze after they have been gritted?”, the wider Northern Ireland context is this: Northern Ireland winter driving is especially sensitive to changing road-surface temperature, rain, ice, flooding and exposed routes. Official advice is to drive for the conditions actually in front of you, not for the posted speed limit or the fact that a road was treated earlier. TrafficWatchNI and current weather warnings are the right live sources when conditions are deteriorating.

For this exact question — “Why can Northern Ireland roads refreeze after they have been gritted?” — the practical point is: Expect ice on bridges, shaded areas and low-traffic stretches even when nearby main roads appear clear. The answer should be applied to the actual signs, conditions, licence wording or parking rules in force at the time, because temporary restrictions and individual DVA decisions can change the ordinary position.

This Northern Ireland-specific page on “Why can Northern Ireland roads refreeze after they have been gritted?” was checked against the attached official sources before publication, with nidirect/DVA and the Northern Ireland Highway Code used ahead of generic UK motoring articles. If the rule, road layout or personal licence condition changes, those primary sources are the ones to re-check.