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.

   https://www.liftedtrucks.com

The logo expressing "Limited Express" is very unspecific, imagine if buses with the Mercedes star cost extra and didn't stop at every stop.

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.

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.

If "drivers of private vehicles in Japan", must understand these "four symbols" then these are not "Japanese symbols that speak without words".

P Plates, Japan