Final answer:
Illinois law dictates that headlights must be on when the weather requires windshield wipers, enhancing visibility and safety on the road without directly observing the bright lights.
Step-by-step explanation:
Specifically, it states that if the weather conditions necessitate the activation of windshield wipers, then headlights must also be turned on. This law is in place to ensure visibility for both the driver of the vehicle using the headlights and other road users during adverse weather conditions, such as rain, fog, or snow. While observing your car's headlights, you should be able to see the lights illuminated without looking directly into the beams, as this can be harmful to your eyes. The illumination of the headlights increases safety on the road by making vehicles more conspicuous. Remember to always follow your local traffic laws to maintain road safety.