Defining a curved path in 3d

We are trying to create a bike driving game.
http://www.kirupa.com/developer/actionscript/shape_camera.htm

This link contains a simple car racing in camera movement.

We want to create something similar to it. but instead of straight road, we need some left and right turns on the road. so that the user bends towards right/ left to take the turn.

somebody pls help,:crying: