Roger:
I would think that the video with photos added similar to the "then and now" threads would add a lot of value to this effort. Since a lot of people have DVD players now either in the vehicle or could download to a tablet etc. the passenger(s) could play and watch as they took the tour.
I also think if you could get a narration with some local RR history/ photos of line in operation etc. from the likes of Earl Knoob (train operations), Ed Trump (MOW & crew) , Ernie Robarts (ralifanning) etc. it would add even more value as you could hear and see the "ghosts" of times gone past.
And lastly, start the video with a map and show the key points of interest on the map that correlate with the mileage from the start point. Maybe at the key points of interest is where the "then and now" would have more information, photos etc. In a way you are doing a modern version of Robert Ormes "Tracking Ghost RR's of Colorado" book just in a video format on the specific route of the Scenic Byway.
My 2 1/2 cents for the day.
Rod Jensen
P.S. Perhaps you can get AAA to underwrite or at least promote this to their membership.