If you read this forum, I posted a method for creating a 3D world with Actionscript. If you are new to Flash, this is a pretty advanced topic. Flash is a vector art program and deals in 2 dimensions only. It is not the ideal program for rendering 3D animation. However, it can be done. The code sample I posted could be adapted to most any kind of game ... from racing to a first person shooter. If you are specifically interested in a 3D Flash racing car game demo, the best I have seen is called "mario kart". You can probably do a google search to find a sample .fla file to explore the methods used to create it, but mind you, they are advanced.
A mind once stretched by a new idea never regains its original dimensions.
- Oliver Wendell Holmes