As a cyclist who wears hi-viz clothing every time I ride (even in broad daylight), I'm somewhat amazed by how many drivers still don't see me. When I have the opportunity I'll ask a driver who clearly missed me what I could have done to make myself more visible, and I am yet to get any actual advice on that. I'm probably about as visible as I can be.

I also have front and back lights (which I only use when dark as I'm not convinced that they help during the day), hi-viz tape covering parts of my bike, and a large hi-viz sign mounted to the back of my bike as a reflector.

A lot of this I think has to do with distracted driving. I've also read that there's a psychological phenomena where someone might be looking directly at something but still not see it because they didn't expect it. So drivers expect cars on the road, not bikes, so making myself brighter might not help. I would need to make myself look more like a car in this theory. I recall reading someone suggest that looking like a person could help, or having motion (i.e., reflectors on your pedals).

Of course, I don't believe that some sort of perceptual blindness is any excuse. Many people would talk about banning self-driving cars that completely missed certain road users, but I'm not sure most drivers would be as enthusiastic about banning drivers who fail the same test.