Driving in fog: speed, lights and following distance

Your speed must allow you to stop within the visible and available distance. In fog, use appropriate lights, increase your following distance, avoid overtaking and do not stop in a live lane; if you cannot continue safely, reach a protected area.

Adjust speed and distance to visibility

In fog, reduce your speed so that the road visible ahead is long enough for you to stop. There is no single speed that works for every foggy condition: visibility, grip, traffic, bends and obstacles all matter. Leave a much greater gap behind the vehicle in front, because sudden braking may remain invisible until it is too late.

Switch on dipped-beam headlights and rear lights as required; daytime running lights alone may leave the back of the vehicle dark. Use front fog lights where permitted and the rear fog light only when visibility is severely reduced, switching it off as soon as visibility improves. Main beam can reflect off water droplets and make it harder to see, so do not use it improperly.

Avoid overtaking and unnecessary lane changes. Follow the carriageway markings without following the lights of the vehicle ahead too closely. Do not use the road edge as a guide if it may contain obstacles or stationary vehicles. On motorways and rural roads, follow temporary limits, variable-message signs and directions from the traffic police.

• Slow down until you can stop within the distance you can see.
• Increase the gap; do not follow the lights ahead closely.
• Use the correct lights; switch off the rear fog light when visibility improves.
• Avoid overtaking and unnecessary lane changes.

When and where to stop

If you cannot see well enough to continue, do not stop in a lane or on the carriageway. Look for a lay-by, service area or another protected place, signalling the manoeuvre in good time. On a motorway, do not get out of the vehicle on the carriageway; if an emergency stop is unavoidable, follow safety procedures and call for assistance. Do not use hazard warning lights while continuing to drive except in situations provided for by the Highway Code.

Once parked safely, decide whether to wait for the fog to clear or change your route. If conditions worsen, do not feel obliged to continue just to keep to a timetable.

To revise the correct use of lights and safety rules,Quiz Patente Ufficiale offers chapters, timed quizzes and review of incorrect answers.