But regardless, you can get an idea from the EU. EU rail subsidies amount to 73 billion euro annually. EU rail carried 465 billion passenger-kilometers in 2017, or 300 billion passenger miles. That's a subsidy of $0.24 euro per passenger mile, even worse than Amtrak.

Roads are just really cheap to build and maintain. A 6-lane interstate highway costs $11 million per mile in urban-ish areas: http://blog.midwestind.com/cost-of-building-road. It's going to cost $1.4 billion to add four lanes to the 35 miles of the BW Parkway (which goes through a dense urban area connecting two major cities). At $40 million per mile, that's 1/6 of what it cost to build the Metro Silver line through less dense areas in an existing freeway median. That's 1/9 the per-mile cost of the purple line, a light rail line that mostly travels at grade without its own right of way.

That's because, even with all its faults, averaged over all travelers it beats the heck out of all the other alternatives for trips that would take more than a few hours by car or train. Scalzi's experience, as messed up as it was, is an outlier.