Perl4Ever was expressing doubt that an area of a million or two people could support rail. I think Kyoto is an excellent counterexample to this claim, and the r

Perl4Ever was expressing doubt that an area of a million or two people could support rail. I think Kyoto is an excellent counterexample to this claim, and the rail lines are what propel the density as people want to buy homes that are walking distance from a train station. But let's look at Boston instead. Population 700,000 in the city limits; 4.8 million in the metro area, so about one seventh lives in the city proper. http://www.rochestersubway.com/images/photos/boston_subway_map.jpg http://www.rochestersubway.com/images/photos/boston_subway_m... While perhaps not as developed as Kyoto, that's still a very healthy rail system. And its first subway was built in 1897 when it had a population of just about half a million.