If you are driving with your high beam headlights on, and get within of a vehicle in front of you, you should switch to your low beam headlights.

500 feet which is the same that 150 meters.

Explanation:

High beam headlights are useful when driving at night or when is difficult to see enough of the road to drive safely. These types of headlights shine twice as far as low beams and allow you to react sooner if any problem is ahead.

They are very useful but if they are used incorrectly they could cause a problem. All the State laws require to switch to low beam when you are within 150 meters of a vehicle in front of you that is approaching or 90 meters behind a car that you are following.

I hope this answer helps you.

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