I use a flag to the side… bus drivers have told me that I should copy write the idea. Then I got a big custom vertical flag, this works even better. Flags have saved my life several times.
I want to make one out of flouresnt yellow-green ripstop.
I have a triangular florescent and reflective flag on the back of my basket and I like it. I see flags on poles that mount on the hub at the local bike shop. They're ok I guess but I wear a vest that is florescent with big strips of reflective ribbon so I am pretty visible.