When is a racer on the right track?

Tonight I had to answer one of the most difficult questions I've ever faced, in game dev. It's this question about how the game will know if the player is going in the right direction, and if the player has completed an entire circuit before incrementing their lap count.

The solution I arrived at (though there's still quite a bit of work left to do) is to "walk the course". This is a process of drawing the waypoint nodes over the circuit, and then firing little projectiles until I've found the next waypoint in the circuit. It's a bit strange, but this is what the process looks like...

I will upload a build (tonight) that includes these collision shapes, so you can see what this first-hand, and then another build (in a day or two) that hides the collision shapes again.

TL;DR proc gen courses are difficult!