this is just a simple small two lain train round-a-bout that I came up with. (I have no clue if this is an new thing or not)

so I was setting up a train station for Iron ore and I need to get more then one iron train on the tracks but when I try to set up holding area for the other iron train to wait in the rail chain signal will always turn red no matter where i put the other rail signal. why is this?