My reading of it is that it isn't the use of symbols that is notable, but rather here are a few handfuls of roles that symbolic decals and signs have been given in Japan, most of which we don't have in North America at least. A lot of them are quite smart. Sure, the special badge for the front of a police or fire vehicle is pretty redundant, but it would be nice if we had a universal understanding of a couple of these just as we understand what the blue handicap icon means. I would nominate the best as:

1. The cross + heart one for people with hidden disabilities. This is probably top of mind for me because I have a family member who could use some extra understanding due to a condition.

2. The new driver, elderly driver, and deaf driver. The first one is obviously so useful that we've just created dozens of one-off text decals (clearly inferior, as they have to be noticed, read, and interpreted, rather than just recognized). It should be handed to you along with your permit and made compulsory like Japan describes.

As for the elderly one, it would be useful to tip us off to give them more space, and also to inspire us to think of our grandmas when we see such a car making a mistake on the road, instead of defaulting to assuming the driver is a deliberately uncourteous prick as we sometimes do.

(As for the "if people are too old to drive correctly, we should take their licenses away" argument, let's assume it's been made, and that someone has pointed out the tradeoffs of that policy in the real world that we live in.)