> (spoiler, 110mph is barely worthwhile and 125mph is an overt waste of effort)

whyfor? I guess I don't know how I would price "get there faster" in a reasonable way.

> separating freight from rail on major routes

that does seem to often be the limiter in North American passenger rail, but I don't know how economically feasabile it is to separate the two. I assume railroads are moderately expensive to maintain.