What must you do if you are driving in a fog and visibility is severely reduced?

When driving in fog with severely reduced visibility, pulling over safely and waiting until conditions improve is the best course of action. Fog can significantly impair your ability to see other vehicles, road signs, and hazards, making it extremely dangerous to continue driving. By pulling over, you ensure not only your safety but also the safety of other drivers.

While it might be tempting to keep driving, moving forward in such conditions can lead to accidents as you may not be able to react to sudden changes. Additionally, using high-beam headlights in fog can create a glare that worsens visibility, while maintaining a constant speed or following the car in front closely can prevent you from having adequate time to react to obstacles. Thus, waiting until visibility improves is the safest decision.