Mostly because it doesn't stay white and looks bad. But it doesn't stop people from painting their siding white, for example.
Why paint the sides of the rails? Well you can paint the tops, but it tends to gum up the wheels and get worn off.
You want a paint with high reflectivity and high emissivity. Just be sure you aren't using infrared light temp measurement as to measure and make claims about differences in temperature, emissivity is something to watch out for when measuring temperature in that way.
20 degrees is surprising, I sure wish my car was white in the summer.
I wonder if you have okay effects with white rails in the winter?
Coverage here: https://velo.outsideonline.com/road/road-racing/tour-de-fran...
But of course, this was done in response to past serious crashes that occured because the asphalt melted. So, it's sort of a damned if you do damned if you dont scenario for the organizers.
This is why truck dock areas are usually paved with concrete.
I couldn't believe the state of US railtrack:
https://www.youtube.com/watch?v=9X2A2f6E5DI
Just go slower! We don't want to pay for maintenance. What's the worst that could happen? You derail and your toxic payload catches fire and poisons the neighbourhood?
https://en.wikipedia.org/wiki/East_Palestine,_Ohio,_train_de...
Am I misreading or does this say the opposite of what they meant?
But the photo caption paraphrases him and says that the white paint fights (as in prevents) the heat, which uses similar words but a different logic to it (but the same overall meaning).
If I've got that right, then I think the blame lies on whoever wrote this article for making it confusing.
https://youtu.be/zqmOSMAtadc?si=UUlmnk9sI-leq0SV
But of course, American infrastructure was built on the cheap, and is not maintained correctly. This is why we can't have nice things.
Your own video points out that it's still prone to trade-offs: rail breaks in the cold are better than buckling in the heat, but what if you could reduce the high point with white paint so you could expand the practical temperature range?