When should fog lights be switched off under the Northern Ireland Highway Code?

Fog lights should be switched off when visibility improves because they can dazzle other road users and obscure brake lights.

The Highway Code permits them when visibility is seriously reduced but requires them to be turned off once that condition ends.

For “When should fog lights be switched off under the Northern Ireland Highway Code?”, 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 — “When should fog lights be switched off under the Northern Ireland Highway Code?” — the practical point is: Reassess visibility as the weather changes instead of leaving fog lights on for the rest of the journey. 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 “When should fog lights be switched off under the Northern Ireland Highway Code?” 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.