japanese lines are more difficult to master because
1. trains from different lines can pull up at the same
platform
2. many suburban lines have through-train services to other subway
lines inside the city itself (due to space constraints, of
course)
3. many different type of services are run on the same line, like
limited express, express, semi-express, rapid, local.
4. some of the fare structure might be different due to the type of
train you choose to take (additional express charge to be shown to
inspector on train)
