When travelling in fog you should reduce your speed. Why is this?

Why that is the answer

Fog severely reduces visibility, making it much harder to see hazards, road markings, and other vehicles ahead. You must slow down so you can stop safely within the distance you can see clearly, as advised by the Highway Code. Although damp surfaces may affect grip, the primary danger is poor vision. Avoid using main-beam headlights, as the light reflects off the fog and will dazzle you.

How this comes up in the real test

Questions from vehicle handling appear throughout the 50-question multiple-choice section, and the wording changes between versions. Learn the rule rather than the sentence: the DVSA can ask the same point from the opposite direction, and a memorised answer falls over the moment the phrasing moves.

The pass mark is 43 out of 50, so seven wrong answers is your entire margin. If a whole category is shaky, run the topic practice below until you are getting every question right for the right reason, then go back to full mocks under the clock.

More vehicle handling questions

• A lot of snow has fallen recently. When driving in these conditions, what are some things to think about?
• After fog has cleared, it can be dangerous to leave your rear fog lights switched on. What is the reason for this?
• What colour are the reflective studs along the left-hand edge of the motorway?
• During the day, when should dipped headlight be used?
• How can you regulate your speed with the engine of your car?
• How should you deal with this hazard?