Have you ever taken a ferry in Japan? The English word feri (ferry) is used in Japan only for boats carrying vehicles. Passenger ferries are just called fune (boats). There are many long-distance ferries passengers can board, however. Traveling by ferry is for those who prefer to travel around Japan rather than barging right through it.
I once took an uneventful four-hour trip from Aomori-ken to Hakodate in Hokkaido on a ferry. It was one of those ferries where the entire thing is like one large billion-mat tatami room where all the passengers sit on the floor.
This is to account for human sprawl, which is kind of like urban sprawl, except that it takes place in large populations riding ferries. You can have hundreds of people sprawled out on the floor at one time. It's almost like a large playroom for kids, who are nice enough to share it with sprawling adults.