Final answer:
Regulations commonly require that headlights be turned on when visibility is less than 500 feet. This safety measure is crucial for seeing the road and being seen by other drivers under poor visibility conditions. Thus, the correct option for when to use your headlights due to limited visibility is A) 500 feet.
Step-by-step explanation:
The question relates to the safety regulations for vehicle headlights in conditions where visibility is decreased. Turning on vehicle headlights is essential for both seeing the road ahead and for being visible to other drivers. Generally, regulatory requirements state that headlights should be turned on when visibility is less than 500 feet.
This is to ensure that drivers can see the road and any potential hazards with enough time to react, as well as to make their vehicle visible to oncoming traffic. Headlights not only illuminate the road during night-time but are also important during adverse weather conditions such as rain, fog, snow, or even dust storms, which can significantly reduce visibility. A driver's headlights need to be functional and used properly to maintain road safety.