UK Driving Theory Practice Exam

Under which visibility condition should you use fog lights?

1. When it's raining heavily

2. When visibility is less than 100 meters

3. When driving through a tunnel

4. When street lights are on

The correct answer is: When visibility is less than 100 meters

Using fog lights is specifically advised when visibility is significantly reduced, typically to less than 100 meters. This condition occurs during heavy fog, snowfall, or heavy rain, as standard headlights can reflect off the fog or precipitation, creating glare and impairing visibility even further. Fog lights are designed to produce a wide, low beam of light that illuminates the road directly in front of you without causing glare, making it easier to see and be seen under these poor visibility conditions. In contrast, using fog lights in heavy rain, driving through tunnels, or when street lights are on does not align with their intended purpose. In heavy rain, standard headlights are generally more effective, while fog lights can be distracting to other drivers. Similarly, fog lights should not be used in tunnels as the illumination provided by them is unnecessary, given that tunnels are well-lit. Additionally, when street lights are on, it's usually sufficient to rely on regular headlights as the ambient light is adequate for safe driving.