When should headlights be turned on at night?

Headlights should be turned on from sunset to sunrise and in conditions of reduced visibility, which includes instances such as fog, rain, snow, or dust storms. This practice is essential for ensuring visibility for both the driver and other road users during the nighttime. When it is dark, the headlights provide illumination, allowing drivers to see the road and any potential hazards ahead. Additionally, having headlights on during reduced visibility conditions helps make the vehicle more visible to others, reducing the risk of accidents.

The other options do not encompass safe driving practices. For instance, suggesting headlights should only be used after two hours of darkness does not account for varying sunset times or visibility conditions that may necessitate the use of headlights earlier. Relying solely on heavy traffic or the presence of other vehicles with lights on does not guarantee adequate visibility, as a driver might find themselves in situations where illumination is necessary regardless of other vehicles around them. Thus, option B accurately reflects the guidelines for safe headlight usage at night and in reduced visibility situations.