Technically, you only need exactly one rail adjacent to a zone in the first game to make it grow, so the entire traffic model can be essentially ignored. Examp

Technically, you only need exactly one rail adjacent to a zone in the first game to make it grow, so the entire traffic model can be essentially ignored. Example: http://www.youtube.com/watch?v=UEzzLXOs-iU http://www.youtube.com/watch?v=UEzzLXOs-iU