Well first of all putting any signals on the single track would only cause instant gridlock – Each train would keep going through the signals of its direction until they would come face to face at a signal in both directions. No way out of it.
And as far as the one direction signals go, I have never been able to make them trigger only in one direction. Every time I connect up a new line to an existing on at the sides, the trains stop at the signals intended for the opposite direction, blocking off the entire network.
Like I already said, Tossi – Your “fix” is just two loops after each other. The exact same thing I showed in my screenshot earlier.
Edit: I give up. We’re obviously not on the same page here – You’ll just have to wait till the game releases and see if you can prove me wrong. (At which point this guide would simply be corrected)