Final answer:
The best rule to follow is to always use headlights when it is raining, snowing, or foggy to increase both visibility and safety on the road. Light rain can make roads slippery with oil and gasoline, while heavy rain may wash some of it away, but driving remains hazardous.
Step-by-step explanation:
The best rule about using headlights on your car is: Always use headlights when it is raining, snowing, or foggy. This is important for safety reasons, as headlights not only help you see the road more clearly, but they are also crucial for making your vehicle visible to other drivers in poor visibility conditions. When the weather is clear, headlights are typically used from dusk until dawn.
However, when it's raining, snowing, or foggy, it's essential to turn them on, even during the day, to enhance visibility and communication with other road users. Note that using headlights is not just for signaling to drivers but is part of safe driving practices to maintain control and visibility.
Driving in light rain can be hazardous because oil and gasoline that have leaked onto the road surface create a slippery layer that can cause vehicles to lose traction. When heavy rain falls, it can wash away the oil and reduce the slippery conditions, although you should still be very cautious due to reduced visibility and potentially standing water leading to hydroplaning risks.