The point isn't that speed limits need to change, it's that it is incumbent upon the driver to slow down if environmental conditions prevent them from traveling safely at the speed limit.
What is that supposed to mean? You can't have 100% safety at any speed. If it really is incumbent upon the driver to always drive at night in such a way that no collision can occur at all, then why not change the speed limit?
My whole point is that it's not the driver's responsibility to account for every possible scenario. It can't be.
Nobody said anything about 100% safety in some provable way. But certainly it is very much the driver's responsibility to pick a safe speed. Driver's Ed (at least in most? EU countries) teaches that the posted speed limit is just that, the maximum legally allowed speed. As a driver you -- and nobody else -- are responsible for picking a safe speed depending on the environmental conditions.
In particular, the following are explicitly taught in Driver's Ed:
1) Don't overdrive your visibility (headlights, curve)... you must be able to look sufficiently far ahead such that you can stop in the event of an obstacle appearing. (In case of two-directional traffic in the same lane, you must be able to stop in half your visible distance.)
2) Reduce speed according to weather: Rain (aqua-planing), Snow/Ice (slippery), Fog (reduced visibility as in 1)
3) You must be aware of situational dangers and be ready to stop if necessary (e.g. parked cars on the side of the road between which children could emerge...)
Nobody else will tell you what the maximum safe speed at any given moment is. You're supposed to learn how to handle your vehicle during driver's ed, and then act accordingly.
Overdriving your visibility is just plain stupid -- you simply will not be able to avoid a collision with an object in time; you're basically driving blind and hoping for the best.
I seriously think you need to retake your drivers ed class. It’s entirely possible to drive at a speed at night that ensures you won’t hit an object immediately in front of you. That’s the textbook definition of not overdriving your headlights. Most nights aren’t pitch black thanks to street lamps, which is why you can drive at a reasonable speed. And in the cases where the night is pitch black, you can use your high beams when there’s no oncoming traffic. If there is oncoming traffic and you can’t stop in the distance illuminated by your headlights then, yes, it’s incumbent on you to slow down. These are basic rules of the road, not some unobtainable standard to strive toward.
I already told you what is safe: Your headlamps must illuminate a distance within which you can stop (including reaction time). With 50km/h this is ~40m. This is a distance that your low-beams will illuminate even in a dark night. If you want to drive faster you need high-beams or some other sources of light (street lamps).
If you don't overdrive your headlamps than objects will not just "suddenly" appear in front of you unless they are doing something genuinely stupid (e.g. jumping in front of the car). In this case the policy or a judge will decide whether you were driving prudent or safe.
We have collisions (during day and night) mainly because people don't pay attention or don't follow some basic rules (visibility, distance to car in front,...). This isn't rocket science. Don't blame fate or "general risk" if you cause a collision.
And lo, that source's number one safety tip for night driving:
> 1. Allow for enough distance to stop. We recommend that you gauge this distance using your headlights. Low beams should allow you to see up to 160 feet away, while high beams should illuminate about 500 feet in front of you. Make sure that, if and when you must brake hard, that you can brake within those distances.
Good start, but that doesn't say that night driving isn't safe. It says that most accidents happen at night. Accidents are rare.
The page also lists drunk and drowsy driving as one of the major reasons why night driving is less safe. These are correlated risk factors, but neither has to do with the conditions being inherently unsafe.
The page doesn't talk about the extent to which drunk and drowsy drivers account for nights being dangerous.
It's not about accounting "for every possible scenario."
Arizona has a Basic Speed Law, which says "A person must drive at a speed that is reasonable and prudent under the existing conditions."
If the speed limit is 55 MPH, but conditions (rain, darkness, etc.) would prevent you from being able to safely stop in time to avoid a collision, then you are not allowed to drive at 55 MPH until conditions change.
My whole point is that it's not the driver's responsibility to account for every possible scenario. It can't be.