Hint for Trainyard level "Three Below"

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?

Solution 1:

My solution relied on three key facts:

• The 1st and 3rd trains, and the 2nd and 4th trains, can be combined. Like Alex says, you can't combine trains that follow each other directly.
• You can safely collide trains (head-on) BELOW the paint blocks since they'll get repainted the way you want as they come back north.
• You need two trains to end up blue, one red, and one yellow, so the blue paint block is key.

One other more explicit hint I can give is that in my solution 3 trains enter the YELLOW paint block going south, and one train enters the RED paint block going south.

Solution 2:

I have the same problem. What I have figured out so far is that you can nver merge 2 trains that come behind the other. So you need 2 blue trains and they can't be both the odd numbered or even numbered trains. I figured out how to get the first 2 trains to be blue and the other 2 trains to be red and yellow, but there is no space left to merge them. I would realy appreciate a hint.