Thanks. I have a couple of questions:

Are logs suitable as barriers for the side of the track? Most people use PVC pipe but it is very expensive, and (this may sound stupid), is also very bad for the environment.

Because I don't have a very large area, I would like to make the lanes 1.5m (5 feet) in width, instead of the normal 2.4m (8 feet). Will this be too narrow? There will be a maximum of three cars on the track at one time.

Should I use wood to make the jumps and then cover the wood with dirt, or should I just make the jumps out of dirt?