But where is it moving to?

Right/entering.

Well, it seems as if it's coming forward as people are standing and waiting for the train.

If you look at the bottom right corner it looks like it is going towards you but if you look at the top right corner it looks like it is going into the tunnel

When you look in the middle right, it looks like it's going back and forth.

You know you can see the girl picture rotating in both directions :P? It takes time but you can switch from clockwise to counter clockwise XD

It changes direction. Just keep looking on the right edge.

The train is just moving back and forth. That's what I'm seeing.

I can make her change direction

someone's been on reddit tonight

Maybe

Actually, all I see is that it goes one way, stops and goes the other way. Like whoever made this .gif did that forward/reverse thing that loops.

It switches from one direction to another.

Away from your thread.