Driving in Fog — How to Stay Safe on UK Roads

Fog creates some of the most dangerous driving conditions on UK roads. The combination of reduced visibility and drivers who misjudge their speed leads to pile-ups that claim lives every year.

The Fog Light Rule

Rear fog lights must be used when visibility drops below 100 metres — roughly the length of a football pitch. Using them above that threshold is illegal and dangerous because they can dazzle following drivers and mask your brake lights.

Front fog lights are optional and should only be used if they genuinely improve your visibility. Many modern cars have automatic lights that don't activate fog lights — check your instrument cluster to confirm they're on.

Speed in Fog

The cardinal rule: if you can't stop within the distance you can see, you're going too fast. This sounds obvious but most drivers maintain motorway speeds in fog because they can see the vehicle directly ahead. That vehicle could brake for a stationary object ahead of them — and you'd have no time to react.

The 'Phantom Gap' Problem

In fog, the tendency is to fix on the taillights of the vehicle ahead and follow them closely. This creates a false sense of security — if that vehicle crashes into something, so will you. Maintain a proper gap regardless of how tempting it is to follow the lights.

Motorway Fog Protocol

In heavy fog on a smart motorway, variable speed limits are mandatory — obey them. If you see a red X over a lane, do not use it. If your car has lane-keep assist or adaptive cruise, turn them off in fog — these systems rely on line markings that may not be visible.

If You Must Pull Over

If visibility becomes too poor to continue safely, leave the motorway at the next junction. Do not stop on the hard shoulder in fog — a following driver may not see you until it's too late.

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