With Google SketchUp, there's no technical terms such as polygon or spline, all that exists is pencil, eraser, ruler, and paper

Seriously, if I created this with 3DSMax, it would take more than just a mere 4 hours! SketchUp will cut/trim the polygon's surface automatically according to your sketch, and this automated process will save you lots of time. I now can concentrate more on the overall track design/layout rather than the technical stuff such as how to weld the vertexes, how to extrude the face properly, etc.
The 'snap-on-everything-on-paper' function also works pretty cool although sometimes can be very irritating if we wanted to place two vertexes very close to each other -they will glued to each other automatically. The snap function also can help us to place a vertex parallel to or perpendicular to faces/points/edges.
The Freehand Tool also works pretty amazing. You can literally paint on the poly surface (vertically or horizontally) and SketchUp will take care of the polygon-cutting transparently.
Track building is more fun with Google SketchUp!

Some people managed to create complex vehicles or buildings with SketchUp. After the track is done, I'm going to make a car with SketchUp.