Some suggestions for updates: Your bridge rails are all polygonal. How about an option to extrude a simple plane or cube with a transparent texture? That should cut down a ton of the poly-count. I like the road options to make it more or less defined (higher / lower poly) so the road itself isn't a major issue as far as performance. Intersections are difficult to work with. I haven't been able to get them to look right on Mac. I know your focus is on realism, but I think a lot of Unity developers will use it for racing games. Could you add a dirt road option? All of the colliders are mesh colliders. These are much more expensive than basic colliders like box colliders. Is it this way so the collider follows the curve of the rails / walls? Is it possible to break those up into primitive colliders? They wouldn't be as exact I imagine, but would save a lot of processing power.