Now available on the Unity Asset Store, a set modular race track pieces and furniture, enabling you to construct your own race course in minutes.
Each track piece is 20m square and fully tileable, allowing them to be used in any combination. Most textures are 1024 wide (2 lower resolutions sets are also included), and every material has a colour, specular and normal map.
Everything shown in the screenshots is included, including an example track.
You can find it in the store here: https://www.assetstore.unity3d.com/#/content/6843
Watch a demo of it here: http://www.rivermillstudios.com/video_race_track.html