I noticed that hi-viz bikers were hard to see when driving in Shenandoah on an autumn day. Not sure what would work in that situation, though.

NYC is full of black-clad, unlighted bikers. I could easily have hit one last night as I passed a runner, and I am careful. I literally couldn't see him with headlights from highway traffic in my eyes.

Hi-viz definitely works in the city. Pll, I agree with you that drivers are more courteous. In addition, I've had various people -- cops, passers-by, etc. -- randomly compliment me on my blazing glory.