Prepare two round cakes. If you are feeding a lot you can do two layered cakes as I did in the picture. If so fill your cakes. Otherwise 2 round cakes one on each side will be fine.
Cut a notch in one of your cakes so the two round cakes fit into each other.
Crumb coat your cakes with chocolate frosting. With a round glass or cup mark two circles in the middle of your two cakes this will be filled in with "grass".
Using tip 233, or you could use a star tip, add grass in the middle of your circles.
Add white piping lines for the road and outline the two round cakes. Add grass all along the edges and add toy cars or whatever details you'd like.