You don't do that speed when other traffic is coming towards you..BUT
Another fallacy. The road that you could see when your headlights were undipped, does not disappear or change position in reality, when you dip them.
Thought wrong, but then that's pretty much a habit with you.
The nature of the exercise is not totally one of absolutes.
You can guarantee to a very high degree of probability that the road hasn't changed just because you cant see it anymore.
You can guarantee that if there are no side turnings, no unlit car (a distinctly rare possibility in the unlit countryside at night) has pulled out in front of you.
So what is left. You know where the road is. You know that nothing you didn't see before is on your side of the road. You know exactly where the oncoming car is.
What is left is the minute possibility that some unlit object has materialised in the road in front of you.
That is small, but not infinitely small. Deer do leap out of hedges BUT if you drive on that assumption, you will, even in daylight, do less than 5mph on any country road. Because that is about as fast as you can go and absolutely guarantee you will never hit a deer.
In general just about any other animal will look at you and its eyes will light up. Pretty visible in any conditions, and whilst it may dent the car, it won't normally kill you. Unless you slam on the brakes and lose control.. I always choose *my* life over a small furry animals, I'm selfish like that.
In addition tree branches DO fall on cars. However they can do that in any light conditions. Round here the wiser drivers note that one or two people a year, driving in gale force conditions, get killed by branches falling on cars. They stay at home.
Slowing down makes remarkably little difference to any of these hazards. The only difference it does make, is when you hit the deer. Over about
60mph it is a very serious accident. So if the road is bounded by the sort of woods that deer like, AND deer are known to exist locally. pushing on much faster than that carries a distinct risk.Which is why, round here, I don't do it.
HOWEVER that isn't the case on other roads.