In what condition are drivers required to have their headlights on?

Drivers are required to have their headlights on when visibility is poor to enhance their ability to see the road, as well as to ensure that they can be seen by other drivers. Poor visibility can be due to weather conditions such as rain, fog, snow, or even smoke from fires, where the natural light is insufficient to see clearly. By using headlights in these situations, drivers improve safety for themselves and others on the road.

In contrast, while it may be common practice to use headlights at night, relying solely on this condition does not cover all scenarios where visibility could be compromised. Heavy traffic, while it may necessitate increased awareness, does not automatically require the use of headlights since it does not directly correlate with visibility conditions. Similarly, driving near schools may necessitate caution and reduced speed, but it does not directly dictate the need for headlights unless the visibility conditions are also poor. Therefore, the correct answer emphasizes the importance of using headlights in situations where visibility is less than ideal.