As a driver you must be able to stop the car in the space you can see to be clear. Therefore the closer the ‘wall’ of fog is the slower you go, 12m (40ft) visibility would be less than 20mph.
Some tips:~
~ Fog can be incredibly dirty so ensure your windscreen is kept clean, before & during your journey.
~ Ensure your headlights & fog lights are working correctly & are clean so you get the full benefit of them.
~ Use your dipped headlights so that the bean aims under the ’wall’ of fog rather than bouncing off it. Fog lights are to be used when visibility reduces to 100 metres or less. This is about 25 car lengths. Of course when visibility improves you must turn your fog lights off so that you do not dazzle other road users & do not obscure the break
lights.
~ Do not hang onto the lights of the car in front, allow a bigger safety gap for breaking & reacting to hazards ahead. The car in front may break very harshly if driving too fast for the visibility.
~ Junctions can be hazardous in fog. You may want wind your window down & listen out for vehicles that you may not be to see. You could also sound your horn to warn other traffic of your presence.
~ Very thick fog can be disorientating. Perception of time changes due to the slower speeds & not being able to see the usual landmarks around you. Allow a lot more time for your journey.
~ Watch for the fog to be patchy, if visibility improves slightly expect it to reduce again as the fog thickens. This can happen surprisingly quickly & the faster you are going the less time you will have to react to danger.
~ Be aware of other vehicles/people/animals on the road which do not have or are not using headlights or fog lights, they can be almost invisible.
~ If you break down, try & get your vehicle completely off the road. Use your hazard lights along with your fog & side lights.
~ It is very tiring to drive in fog so take regular breaks to rest your eyes.
~ Be aware that the longer you drive in fog the more accustomed to it you get. The speed can creep up so keep an eye on the speedometer so that you can ensure that your speed is within the braking distance of your visibility.