In most states it is 500 Feet. Common sense should prevail.
300 feet
at least 2m
500 to 1000 ft.
in florida you must dim your headlights from the oncoming traffic at 500 feet. and from the rear at 300 feet.
Be considerate in using your high beams. Your headlights must be on low beam when you are within 500 feet (150 m) of an approaching vehicle, or within 200 feet (60 m) of a vehicle ahead of you, even if the vehicle ahead is in a different lane. You should also dim your lights for pedestrians approaching you. http://www.nydmv.state.ny.us/dmanual/chapter10-manual.htm (Alaska and Oregon are the same as New York - 500 feet.)
If you can see the area lit by their headlights, then you are probably close enough to dim your own.
Dim headlights form high beam to low beam
Turn off headlights and leave parking lights on.
Turn off headlights and leave parking lights on
Turn off headlights and leave parking lights on.
turn off headlights and leave parking lights on
according to Florida handsbook, you must dim your bright headlights within 300 feet of the vehicle ahead.