Some of that may be a difference in focus. The L barely extends outside of the city proper, and a separate rail system almost exclusively serves the suburbs. T

Some of that may be a difference in focus. The L barely extends outside of the city proper, and a separate rail system almost exclusively serves the suburbs. The division of responsibilities between the rapid transit and commuter rail systems in DC and the Bay Area is different in a way that might account for both the greater total system length and the lower ridership per mile compared to Chicago's system. Or Boston's T, for that matter.