500 to 1000 ft.
at least 2m
according to Florida handsbook, you must dim your bright headlights within 300 feet of the vehicle ahead.
If you are a courteous driver, you will dim them when you see their tail lights. No one likes bright lights in their mirrors, reflecting into their eyes.
If you are driving with your bright lights on and can see an approaching vehicle, you should turn off your bright lights immediately.
The law in most states is between 300 and 350 feet. Personally I do it as soon as I can see the tail lights simply because it bugs the heck out of me when someone comes up on me with their bright lights on.
Although the lights should be dipped when approaching another vehicle so they aren't bright, the best place to look would be at the edge of the road on your side; you will still be able to see most of what is on the road ahead of you, but without looking directly at the bright lights.
500 feet is what I was taught but different areas have different rules. You may have to check with the DMV or the PD about this.
If you can see the oncoming vehicle then he can see you. Dim your lights at that time.
It perfectly depends on where you live or drive. You should dim your headlights right when you see another vehicle in front of you or right when you see the lights of another vehicle. It doesn't matter if you are seeing the tail lamp (both of you are traveling in the same direction), you should dim the lights or else it is going to make difficulties for the driver in front.
500 feet if the vehicle is coming to you, 300 feet if you are following it.
The word bright is an adjective, a word that describes a noun. The word bright is also a noun, a singular, common, abstract noun; a word for and intense color or light, a setting for headlights on a vehicle, or a type of tobacco.
As soon as the on coming traffic comes into view.