> bullet trains are great but I fully support the ability of individuals to pay to access freight or passenger rail to subsidize the infra.

It’d be even nicer if you could hook your private car to a bullet train.

Unlikely. Because they tend to be close-coupled units with distributed power and traction control. In case of anything Talgo-related with https://en.wikipedia.org/wiki/Jacobs_bogie 's even more so.