Path Constraints

Path Constraints constrain an object's motion to a predefined path.This type of animation is good for cars and planes.
I firstly began by creating  a spline and joined it up again and closed the spline.
I then clicked Edit,Select All.

I then clicked Line,Render,enable in Renderer.I then added the standard primitive, A teapot.I then changed the parameters and changed the segments for 4 to 6.Then changing the viewport to edged faces.

I then clicked motion,asign controller,position position.A box will then appear to display position controllers.i then clicked path contraint,Ok.I then clicked Add path.

Once I clicked play the teapot followed around my spline.