Following in the vein of this question, I am having trouble with the Trainyard level "Three Below" (located under Bonus Levels, in Toronto).
Many of my attempts end up with the Blue trains 1 square away from the Red/Yellow trains, so I can't merge them. Other times, I break it down into left half (Purple) and right half (Green) - when I do this, I successfully get one side solved but attempts to get the other side solved mess everything up.
What am I missing, here? Got any tips, without spoiling a full answer?