Which of these is a lawful use of high beam headlights?

Using high beam headlights on unfamiliar rural roads is a lawful use because such areas often have limited or no street lighting, making visibility crucial for safety. High beams can help illuminate the road and any potential hazards farther ahead, which is particularly important when driving in areas where you may not be familiar with the terrain or presence of wildlife and other obstacles.

In contrast, using high beams in foggy conditions can actually reduce visibility because the light reflects off the moisture in the air, creating a glare that can make it harder to see. In heavy traffic, using high beams can blind other drivers, increasing the risk of accidents. Additionally, using high beams in well-lit city streets is unnecessary and can also create glare for other road users, detracting from safe driving practices. Therefore, the appropriate use of high beams in rural areas enhances visibility while minimizing risks associated with poorly lit conditions.