II think it's actually pretty easy to understand just by comparing the US to a country with a useful passenger rail system. I'll use Germany because I've spent

II think it's actually pretty easy to understand just by comparing the US to a country with a useful passenger rail system. I'll use Germany because I've spent some time there and taken a few trips by train. Two things are required for a regional or national train service to be useful enough that it can be self-sustaining: population density and local public transportation. Local public transportation also requires population density to be effective; someone considering taking a train to Tallahassee FL might decide to drive instead after looking up the bus schedules online. Busses run about once an hour during the hours people normally commute to day jobs and do not go to many useful locations, like the airport. Germany has a population of about 80 million people. Germany is smaller than Montana. The US as a whole has 26 times the land area but less than 4 times the population. There are useful train services in population-dense areas of the US such as the SF bay area and the NYC/northern New Jersey region. The population density of these areas is such that it's often easier to travel by train, subway and bus than by car. The same is not true of Billings, MT, the largest city in a state bigger than Germany. The population of Billings is about 100,000, and the closest city in the state with a population over 10,000 is Bozeman, about 150 miles away. The population of the whole state is about the same as the city I live in, Jacksonville FL, and that city can barely sustain a barely useful bus system. If the US is to have a decent nationwide public transportation system, it needs about a billion more people. I'm not sure we actually want that.