Hello! I'm sure this is easy, but I can't figure it out. I just want the vertical lines (on the sides of the race track. See attached)) to "go back" in 3d space ... But, I want the stroke widths to staty the same. I thought I could do it with the Repeater, but no luck so far. Any ideas?
You can use the Taper function on stroked paths to simulate an object receding into the distance.
But, depending on what you're trying to achieve, it might make a lot more sense to build your environment in 3D, rather than simulate it. Here's two straight stroked paths, rotated in 3D so that they naturally recede into the distance. Working in real 3D space will give you much more opportunity to interact with other elements in 3D space, plus the ability to light, add depth of field etc.
With thin lines such as yours you're going to run into all kinds of trouble, no matter what the method, but yes, as Andrew suggested, using AE's native 3D capabilities, limited as they may be, would likely be a better way to go about this. Otherwise you'll have to do it the old, hard way and animate the parallax scrolling by hand or using expressions on individual layers.