I have come with an idea(probably not original

) for a simple modual track. it is what ever dimensions you can afford to have.
what my idea is, is to have a modual track that is easiley transportable, dosent take up much room, but can be made bigger, and is realativly easy and cheap. so i came up with the idea of have whatever type board you want for track, i would probably go with mdf or something, and in what ever size you want. i would have it foldable, so i could fold it in have to transport it/store it. i would have the "barriers" be pegs that stick into holes on the board, and have velcro around the pegs. and to block off a section, you could take velcro strips and wrap it around the pegs. I know its not very well explained, so heres a pic.
The yellow things would be the pegs. my board would be 4' x 4' and the pegs would be about 9 1/2 inches apart.