There is a train roughly every 3 minutes
There are two tracks and two trains (one on each track) that shuttle back and forward
The idea really is that one train leaves C and one leaves A at the same time. They pass at B.
How frequently would you like the trains?
If they put on more trains, they would run them all down one line and back up the other. I am not sure you would be able to make them more frequent with having to change points ,spacing etc