My understanding of train lines in America is that lots of them went to ruin and the extant network is only “just good enough” for freight. Nobody talks about Amtrak or the Southern Belle or anything any more.
Air travel of course taking over is the main reason for all of this but the costs sunk into the rails are lost or ROI curtailed by market force and obsolescence.
Completely relevant. It’s all that remains of the train tracks today. Grinding out the last drops from those sunk costs, attracting minimal investment to keep it minimally viable.
Grinding out returns from a sunk cost of a century-old investment is pretty impressive all by itself.
Very few people want to invest more: the private sector doesn't want to because they'll never see the return, the governments don't want to because the returns are spread over their great-great-grandchildren's lives and that doesn't get them re-elected in the next n<=5 (because this isn't just a USA problem) years.
Even the German government dragged its feet over rail investment, but they're finally embarrassed enough by the network problems to invest in all the things.
That's simply because capitalists really don't like investments with a 50 year horizon without guarantees. So the infrastructure that needs to be maintained is not.
Air travel of course taking over is the main reason for all of this but the costs sunk into the rails are lost or ROI curtailed by market force and obsolescence.