[erispoe]

> Retrofitting modern (past century technology) transport systems onto cities that are a ~ 1,000 years old is things that many cities have managed to do. Almost any capital city in Europe would make a good example.

These cities have always been pretty dense. Density around transit stop is the critical dimension of successful transit systems. Building infrastructure is a pretty trivial problem in comparison of changing the density distribution of a whole metropolitan area.

It can be done, however, with enough political clout. Many American cities have a big advantage: large straight streets. Car lanes can be converted to transit lanes for cheap, but it's politically very hard to do.