In the 10+ years I've been running a UI/UX design firm for software companies, I've come to the conclusion that icon design, is not very different from logo design and brand design. A Nike swish logo by itself, without context of the brand we have with it today, is just a random piece of graphic. The pixels itself are worth practically nothing. But because when we see the Nike logo, we feel something (Athleticism, motivation, inspiration, energy, etc.) the mark is worth billions. The magic is not in the mark itself, it's in the context and meaning it builds up in the user's mind over time. Same goes for icons. When seeing a play button with a red background and a white triangle, it might suggest you're looking at a Youtube video. Icons, have no real meaning or worth without context that's built up over time. Both are 'investment graphics'. So the purpose of an icon should be to make the user familiar with something and initiate a mental model when you see it (You see Nike, you feel something. You see a Play button, you know you need to click it, etc.). Don't judge icons by their looks, but by their context. In other words: Can the icon you are adding in your UI, over time and by continuously link the mark to a specific outcome, make the product easier to use because it instantly gives the user a mental model of it's meaning and consequence when clicked.
And some tape decks supported playing the other side of the cassette without flipping, so had a second play button with the arrow reversed, or for those that did it automatically, one button with both arrows.
Wow, I completely forgot about that fact. So the play triangle was an arrow saying "tape is rolling in this direction" and fast-forward and reverse double triangles were "tape is rolling fast" in the respective directions.
Did these buttons first show up on cassette players? The reel-to-reels I can think of had multi-position switches.
I looked it up and they date back to the 1960s on reel-to-reel tape recorders. The pause button was added later when companies found that they couldn't properly translate the word pause into every language. The idea is that the two bars look like the square stop button and look like a frame stopped while it is rolling to the next frame. The reasoning behind the square is that it's the play triangle without a direction; it is stopped in both directions.
I think many traffic signs are visual. Ie they would not work as well if you did random assignment of sign graphics vs its purpose.
Not all of them are, of course.
For a very basic and obvious example, possibility to turn right vs turn left signs look different not just because of convention but they resemble the shape of the road.
I'm with you on the context issue. Funny thing is as soon as OP ranked the dash icons in order of clarity, the very first one - right arrow, ranked "clearest" - I had no idea what it was. I had to think for a sec and realize it was a turn signal. For me, without that symbol being shown specifically on the right side of the cluster, with a big steering wheel in the middle, it loses a lot of meaning.
There are a lot of interesting case studies I remember reading about logos about 15-20 years ago, where the big thing was dropping the company name from the logo and using the logo image only. A couple of the examples I recall are target, Starbucks and maybe McDonald's. A lot of this was justified on "globalism", to your point, where the logo conveyed the brand universally unlike a company name or tag line.
One thing to be aware of with both names and logos, is potentially what the name/logo may mean in other places throughout the world.
Thanks for your insight, you should write articles/blogposts about that aspect of UI/UX business that rarely talked about unfortunately. Icon relevancy is contextual, that's an important concept.
To go further with the idea of context, a square on its own is meaningless, a square next to a circle and a triangle means stop, next to play and record.
And it's also these relationships that will tell the user what to click on.
