It was very surprising for me when I visited the US to see just how much space was wasted writing everything out on every sign and sometimes in giant words on the road.
It did also make me a bit worried about the expected level of driver education...
The common theme for the discussed symbols is consideration for others.
In New Zealand we require a yellow [L] sign on cars with learner drivers (with learners drivers licenses). However I get the impression that other drivers are less considerate around a car displaying the [L] sign.
I suspect New Zealanders are generally far less considerate than Japanese. Politeness avoids a trillion sharp edges.
We also seem to be copying some of the US predilection of arsehole Ute (pickup) drivers.
Very interesting but the comparisons are somewhat US-centric. For example, there is an equivalent to the heart and cross in some western countries which is the sunflower lanyard.
Interesting that a lot of US road signs have words on them: https://ygraph.com/graphs/roadsigns-20120316T030941-ekrruua.... , or are obvious, whereas in Europe drivers need to learn what they mean: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh...
For example the yield triangle, no stopping and no parking are probably unfamiliar to US drivers.
Meanwhile all Alfa Romeo Quadrofoglio drivers might be mistaken for drivers with missing limbs in Japan.