Wet weather
Spray can reduce visibility, especially at higher speeds. Use dipped headlights, reduce speed and leave at least double the normal separation distance.
Ice and frost
The safest advice is not to drive unless necessary. Allow up to ten times the normal braking distance and use controls gently.
Fog
Use dipped headlights, slow down and leave plenty of space. You must be able to stop within the distance you can see to be clear.