Idaho Written Driver's License Practice Test

When driving through heavy daytime fog, should you use high beam headlights?

1. Yes, to see further

2. No, they can cause glare and reduce visibility

3. Only if it's very dense fog

4. Always use high beams in adverse weather

The correct answer is: No, they can cause glare and reduce visibility

Using high beam headlights in heavy daytime fog is not advisable because they can create a blinding glare. When high beams are activated, the light is projected forward and reflects off the water droplets in the fog, creating a wall of bright light that impedes your ability to see clearly. This glare not only makes it difficult for you to see the road but can also affect other drivers, worsening overall visibility in the foggy conditions. Instead, low beam headlights are recommended when driving in fog. Low beams are directed more towards the ground and reduce the amount of light that will reflect off fog, mist, or rain. This enhances your visibility and allows you to see the road and obstacles more clearly. Understanding these principles is crucial for safe driving in adverse weather conditions, particularly fog, where visibility is already significantly limited.