Final answer:
When on an open highway, headlights should generally be dimmed within 500 feet for a following vehicle and within 1000 feet for an oncoming vehicle. These distances ensure safety for all road users and are typically outlined in local driving regulations, though they can vary by location.
Step-by-step explanation:
The question of when to dim headlights on an open highway for a following or meeting vehicle does not have a universally fixed distance; however, it is generally recommended by many driving manuals and state laws to dim your headlights within 500 feet when following another vehicle and within 1000 feet when approaching an oncoming vehicle. These specific distances may vary based on the region and local laws, so it's essential to be familiar with the rules in your area.
For example, when considering safe distances to cross in front of a moving car, one would need to ensure a sufficient gap allowing adequate time to reach the other side of the road safely without getting hit by the vehicle. Understanding the speed of the oncoming vehicle, its distance, and your walking speed is critical. If a car is 28 meters away, equivalent to the length of about 8 average cars, and traveling at a typical town speed limit, you'd likely have enough time to cross, assuming a normal walking speed.
Finally, having an understanding of the headlight brightness and the power consumption of car headlights, such as the '12-V headlights rated at 40 W' scenario, can help estimate battery life in the event that lights are left on accidentally. This is a practical consideration related to headlights and automobile maintenance.