The DTC
Driving Conditions6 min read

Driving in Fog, Mist & Low Visibility

Fog can reduce visibility to a few metres. The examiner wants to see you slow down, use the correct lights, and maintain a safe gap when you can barely see the vehicle ahead.

The full guide

Fog is one of the most dangerous driving conditions because it reduces visibility to a fraction of normal levels. At 30 mph, you travel nearly 14 metres every second. In thick fog, you may not be able to see 14 metres ahead, which means you have no time to react. The examiner wants to see you adapt dramatically to these conditions.

The first rule of fog driving is to slow down. Drive at a speed where you can stop within the distance you can see to be clear. If you can only see 50 metres ahead, you should be travelling at a speed where you can stop within 50 metres. This is typically below 30 mph. Never use the vehicle in front as a guide — they may brake suddenly or leave the road.

Use the correct lights. Dipped headlights must be used in foggy conditions. Front fog lights can help you see the road edges more clearly but only when visibility is below 100 metres. Rear fog lights must be used when visibility is below 100 metres, but switch them off as soon as conditions improve — they are extremely bright and can dazzle following drivers.

Do not use full beam headlights in fog. The light reflects off the water droplets and creates a white wall effect, making it even harder to see. Dipped headlights and fog lights are the correct combination.

Maintain an increased following distance. You need more time to react because you cannot see hazards ahead. Use the road markings and reflective studs to keep your position. On motorways, follow the left edge of the lane using the reflective studs — red on the left, white in the centre, amber on the right.

Common faults

  • Driving too fast for the visibility in fog
  • Not using dipped headlights in foggy conditions
  • Using full beam headlights, which reflect off fog and reduce visibility
  • Following the vehicle ahead too closely as a guide
  • Not using rear fog lights when visibility is below 100 metres
  • Leaving rear fog lights on after conditions improve, dazzling other drivers
  • Not increasing following distance to allow for reduced reaction time

What the examiner looks for

  • You reduce your speed so you can stop within the distance you can see
  • You use dipped headlights and fog lights correctly
  • You do not use full beam headlights in fog
  • You maintain a safe following distance despite reduced visibility
  • You use road markings and reflective studs to stay in lane
  • You react calmly to sudden changes in visibility and traffic flow

Quick tips

  1. 1If you cannot see far enough to stop, you are going too fast — reduce speed immediately
  2. 2Use dipped headlights, not full beam — full beam reflects off fog and blinds you
  3. 3Front fog lights help below 100 metres visibility; rear fog lights are mandatory below 100 metres
  4. 4Switch off rear fog lights as soon as visibility improves — they dazzle following drivers
  5. 5Follow the reflective studs on motorways — red on the left, white in the middle, amber on the right

Common questions about driving in fog, mist & low visibility

How fast should I drive in fog?
At a speed where you can stop within the distance you can see to be clear. In thick fog where you can only see 50 metres, you should be travelling at no more than 30 mph. In very dense fog, you may need to drive at 20 mph or below. Never use the vehicle ahead as a guide.
When should I use fog lights?
Front fog lights can be used when visibility is below 100 metres. Rear fog lights must be used when visibility is below 100 metres. Switch off rear fog lights as soon as conditions improve — they are bright and can dazzle drivers behind you.
Why should I not use full beam in fog?
Full beam headlights reflect off the water droplets in fog, creating a white wall effect that makes it even harder to see. Dipped headlights point lower and reduce this reflection, giving you better visibility of the road ahead.
What if the fog suddenly gets much thicker?
Reduce your speed immediately. Turn on your fog lights if visibility drops below 100 metres. Increase your following distance. If conditions become too dangerous to continue safely, find a safe place to pull off the road — a service area, lay-by, or side road. Never stop on the hard shoulder of a motorway unless it is an emergency.
Can I use my hazard lights in fog?
Only if you are stopped or moving very slowly and creating a hazard. Hazard lights should not be used while driving in fog because they can confuse other drivers about your intentions. Use dipped headlights and fog lights instead.
How do I stay in lane in thick fog?
Use the road markings and reflective studs. On motorways, follow the left edge of your lane using the studs — red on the left edge, white between lanes, amber on the right edge. Do not fixate on the vehicle ahead — maintain your own lane position and safe speed.

Ready to put this into practice?

These guides are a great starting point, but nothing replaces working with a DVSA-approved instructor who can give you real-time feedback.

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Driving in Fog, Mist & Low Visibility | The DTC