In my part of the world there is a book available called "Motorcycle roadcraft" which is intended for police motorcyclists.
It explains in great depth , and repeatedly, why roadusers do not "see" motorcyclists.
After reading it from cover to cover a number of times, and having been the victim of a driver who looked straight "through me" and pulled out on me leading to a nasty collision, I now understand that drivers brains sometimes may not register your existance.
If there is no signal to the brain that you are there, you might as well not exist to that driver at that instant.
The good news is that there is stuff we can do. There is the usual High visability clothing, meaning the real thing, day glo green, not a bright shirt... but we can do better.
A headlight is seen as an annoyance by the brain and if there are two bikes or a car behind you may be interpreted as one car. No bike exists....
This is why twin headlamps are so dangerous on bikes, especially at night, a driver from a side road will interpret your two lights as a very distant car, not a close up bike, and will pull out, you will hit him, and everyone will wonder how on earth it happened. For the rest of his life he will say "I never saw him", which he did n't, or "he came out of nowhere" , which he did,, he saw a non existant car a mile away.
This is something you can prove. Have one of a group of bikes have something "diferent" on his bike. Lets say a high speed flashing led white light showing at the front, the sort of thing a cyclist might use at night and pay a few dollars for. He is the one you see. Yes the others are there, but your brain sees the unusual.
There is another really good tactic which is recommended to Police riders. If you are on a right of way road and someone is waiting at a side road, make eye contact, and when you do, move your bike sideways just a little away from his side. Suddenly you are "unusual" to his brain. His brain will register the "across the field of view" movement, and wow, he sees you . If you ride in a straight line he may look through you, or rather his brain will. He will not have commited a mortal sin, he may not even have been careless, his brain will just have failed to record you as a moving machine.
Having read this book, I now treat every traffic conflict as a potential accident, and far from spoiling my riding, it makes me feel more involved.
I like to actively get seen, and let everyone know "I am looking at you, and you have seen me".
Sorry for going on.