It would be interesting to see actual numbers and you seem to have studied this a bit.
https://books.google.com/books?id=jJGZDgAAQBAJ&printsec=fron...
Back when "peak oil" was a thing, I was in several discussions about what it would take to electrify the US transportation networks, both passenger and freight, but I have not worked in transportation planning. Hydrogen-fueled intercity buses will be much easier to implement than anything else, especially if they are autonomous to reduce driver costs.
It only lists raw energy use and not greenhouse gas emissions though. I'm a bit surprised since the tables I've seen have train emission at the very bottom, but most of what I have seen is from Europe but we run diesel trains here in Norway too (in the north) and the tracks are not straight at all!
Rail: 28 g/passenger km Air: 244 g/passenger km (road 101 g/passenger km)
2014 figures. Edit: Units !!