In an extension to the OP's question, what is the correct way to warn oncoming drivers of danger ahead at night time?
The other night, on a dark country road, on a foggy night, I came across a car that had spun out on a corner and had it's nose in the ditch and tail out in the coming lane on a blind corner. The people had help on the way so didn't need anything from me but were worried someone was going to come around the corner and crash into them. So I continued and flashed oncoming traffic up the road - short blips of high beam. Some people misunderstood, got angry and fully high-beamed me. No doubt they figured it out around the corner, but it would have been too late.