It would need different modes for authoring. One would be full blown detail. You draw out everything, including the birds sitting in trees, and how deep the buildings go.
But a quicker, simpler mode would allow you to just lay track, and the computer would generate the background, fencing, and rumble strips. It could even smooth out the road to make it more 'drivable', to make it flow better.
I guess this would also let us build tracks that have virtical loops and twists. We could see which cars had the best down force ... or is it UP force when you're upside down? (:
~LoudMusic