I'm sure there something useful in your model, but we won't get to it by quoting our favorite and unfavorite road and rail journeys at each other (Guilty, Yer Honner). Is it fair to compare 1->2 track rail with a 4->6 lane highway upgrade? Shouldn't we be looking at 1->2 (roads and rail with sidings or turn-offs) or 4->6 for both modes? Are there any long-distance 6-track rail corridors anywhere in the world? Isn't it simply the case (as someone mentioned) that dual-track standard-gauge rail was hugely overspecified for the needs of 150 years ago, and now we have a fair amount of legacy single track that can be upgraded at relatively modest cost because the ROW is wide enough for 2 or 3 tracks, or can easily be enlarged because it's in remote areas?

I'm about to relocate to a job in the suburbs of pre-WW1 megacity. My plan is to live in a walkable central neighborhood with redundant rail links to my place of work (reverse commute), and to manage without a car. So I'm on your side: I just think you could make your case better - and I'm sure you will.