Comment by kartickv

I'm not convinced that buses don't have the capacity trains do, when you consider that headway between trains is at least 90 seconds. If headway between buses is three seconds, in those 90 seconds, 30 buses can pass by. Assuming a bus has roughly the same capacity as a coach in a train, and that the train has 8 coaches, buses have roughly 4x the capacity.

Not to mention that buses can serve many routes that don't have enough capacity to merit a train, bus routes can be reconfigured without it taking years, and a bus system doesn't cost billions upon billions of dollars to build. Heck, even a single line of a metro system can cost a billion dollars to build.