Met Office advice for travelling in foggy conditions says that it can be extremely dangerous, as fog can drift rapidly and is often patchy, leading to unpredictable conditions.
The Met Office advice to road users is to avoid travel if possible, and to drive very slowly with dipped headlights and fog lights. Driving with headlights on full beam is dangerous as the reflection can cause a 'white wall' effect.
They further advise that if you must drive, keep extra distance between you and the car in front, as the sight of rear lights can give a 'false sense of security'. You should keep an eye on your speedometer, as driving through thick fog can create the illusion of moving slower than you are.
Finally, be aware of the risk of freezing fog, which can form a layer of ice on your car and the road rapidly, creating dangerous driving conditions.