Which action is NOT appropriate when driving in fog?

Using high beam headlights in foggy conditions is not appropriate because fog can cause light to scatter, making visibility worse rather than better. High beams shine light upwards, which reflects off the fog and creates a glare, further impairing a driver's ability to see the road and any potential hazards.

In contrast, reducing speed is a sensible action because it allows a driver to react more quickly to reduced visibility and potential obstacles. Using low beam headlights is recommended in fog as they illuminate the road directly in front while minimizing the glare caused by reflective moisture in the fog. Increasing following distance is also critical, as it provides more time to react if the vehicle in front suddenly stops or slows down, which is more likely in low visibility situations.