I suspect flashing a stop sign sized image of a stop sign for 500ms on a tv mounted where the stop sign goes, at an intersection that should probably have a stop sign, would get most people to stop.
I thought the same thing and most certainly slow way the heck down while trying to figure out what the heck I just saw. I'd probably presume it was some sort of programmable temporary signage on the fritz and treat it like a traffic light with the lights out.