Exercise 1: sample answer

Most of Japan is mountainous, so people and cities are packed onto a few coastal plains, and a railway can move huge numbers of people through a narrow space far better than roads can (check the share of mountainous land). The big cities also lie along one long corridor, which makes a fast trunk line especially valuable. Scotland has a smaller population spread across large rural areas and two main cities close together, so its rail demand is much lighter and more focused on a few routes.