> Direct bus lines don't scale. As the city grows large enough, you have to replace them with trunk lines. If you have a route that has hundreds of thousands o

> Direct bus lines don't scale. As the city grows large enough, you have to replace them with trunk lines. If you have a route that has hundreds of thousands of people going in the same direction, true enough. However, America has very few of those routes, even in big cities well-served by transit. NYC obviously has extremely high density and is very well-served by successful transit. Outside of NY, there aren't many success stories. The busiest light rail line in San Francisco serves ~60,000 riders/day, and most of the others serve far less. Caltrain serves ~20,000/day. BART serves about 100,000/day on its routes, 400,000 in total. And that's the second most-dense city in the US. Because of the land use, there is basically nowhere in the United States that can support a viable rail system. There are systems that kind-of-sort-of work -- like SF BART, Portland TriMet, DC WMATA, Boston MBTA, Chicago CTA -- but none of them are very good, and they never will be, nor can they be (excepting maybe CTA), without completely changing the land use in this country. The problem is that America keeps cargo culting rail systems in areas where there is just zero chance for them to ever be effective, like Sacramento, Salt Lake City, Honolulu, Los Angeles, etc.