There are different ways of doing this.
E.g. skewing 2d sprites to create arbitrary polygons, to get a 3D perspective.
You can also rasterize the polygons yourself.
As usual, google has some good resources on making games:
http://www.extentofthejam.com/pseudo/
The first link helped me a lot when I did a racer a couple of months back. I chose to rasterize the image myself.
It’s not terribly complicated, but in the end I also got performance issues, since I modified a buffer, and set a texture every frame, pixel-by-pixel from Lua ^^
Next time, I’ll move that code to C++ and do the rendering there instead.
As for physics, the game logic is in 2d (top down), with each object (car/bonus) represented as a box.
With so very few obstacles, it’s easy to do a box-box check yourself.
The background, sun+mountains (made by @Axel), and the objects are made of sprites so it’s only the road and the sides of the road that is rasterized.
