Funeral cortege etiquette

There's a funeral procession going by my house, and all the cars have little yellow signs or purple flags on top of the car. I'm glad they do: not only is it rainy here today so lots of people have their headlights on, but so many cars now have automatically-on headlights, it's not easy to tell. I remember being in a procession, properly "running" the red light with the rest, and wondering how anyone who'd missed the hearse at the front would know that I was not just being a jackass. (Also noted: the hearses had flashing headlights.)