Philadelphia Drivers License Practice Test

Should you use high beam or low beams in fog?

1. High beams

2. Low beams

3. Fog lights only

4. Turn off all lights

The correct answer is: Low beams

Using low beams in fog is the appropriate choice because fog can scatter light in various directions, causing a glare that can impair your vision. When high beams are used, the light is directed upward, reflecting off the fog particles and creating a bright glare that makes it even harder to see. Low beams, in contrast, emit light that is closer to the ground, providing better visibility without contributing to the fog's reflective glare. Fog lights, while useful for improving visibility in dense fog, are specifically designed to cast a wide, low beam of light that illuminates the road immediately in front of you, showing you the edges of the roadway while reducing the amount of light that hits the fog directly above. Turning off all lights is not advisable when driving in fog, as this could make it difficult for other drivers to see you, increasing the risk of an accident. Using low beams allows for safer navigation in these conditions without the added complications that high beams create.