Flashing traffic lights--yellow/yellow?
In a discussion on another board about how to proceed at an intersection where the traffic light is flashing yellow, a couple of people claimed to have seen lights flashing yellow in all directions. I have only ever seen yellow/red (i.e. traffic for one direction-- e-w or n-s --has yellow and cross traffic has red) or all red, and it's always been my assumption that that is built in to their design, since the usual driver's ed instruction is to proceed with caution on a flashing yellow and stop on flashing red. Google isn't helping me much here, so I'm hoping we have somebody here who actually knows something about this. I don't know enough about how traffic signals work to really argue this point, so is it possible for a malfunctioning light to flash yellow/yellow rather than yellow/red or red/red? I'm sure there could be some massive malfunction that could cause pretty much anything to happen, but I mean in the most likely malfunction conditions, is it possible?