The best candidate for a twice daily service would have to be the fact that it would provide the greatest good for the most amount of people, or utilitarianism. I think that the current ridership trends plus the boom in the Bakken field necessitates a second frequency. An option for this that I went for was to have one of the trains run to Seattle, and the other to Portland. On the Portland train - I had it closely mimic the current calling times in order to keep the Coast Starlight connections in both directions. Also having the trains not separate and attach saves time in Spokane. The Seattle run is also timed fairly strategically as well. Going east, it arrives Everett in the morning with a little time to spare so to allow a connection from the morning southbound Vancouver run, assuming that time can be shaved off the schedule north of Bellingham if the US Immigration people can preclearing everyone in Vancouver. It then provides daylight service to Spokane, and allows people to arrive in Whitefish at 11PM so that a coach ride would be tolerable. It hits the Bakken oil field in the late morning, and then allows a daytime run from those ND cities to the Twin Cities. It then provides an overnight frequency Twin Cities to Chicago. Same stuff is in effect in the other direction. There is a basic 45 minute pad at each endpoint here. The equipment, to be utilized more effectively, should rotate between the sets. The Seattle set would arrive Chicago at 7:15am, then leave for Portland at 3:15pm. The Portland section would arrive at 2:45pm, and leave for Seattle that night at 11:15 pm. This allows for better utilization while still having plenty of time at each end to be serviced. I assume a consist at that point would be something like P42DC, P42DC, Viewliner bagdorm, Superliner Transdorm, Sup Sleeper, Sup Sleeper, Sup Diner, Sup SSL, Sup Coach, Sup Coach, Sup Coach, and then maybe a fourth coach depending on the time of the year. Seems pretty good to me
9:00A Seattle, WA 5:30P
5:00P Portland, OR 9:00A
5:00P 12:30A Spokane, WA 12:45A 8:45A
11:15P 6:45A Whitefish, MT 8:30P 4:30A
4:45A 12:15P Havre, MT 3:00P 11:00P
10:00A 5:30P Williston, ND 11:45A 7:45P
12:15P 7:45P Minot, ND 9:45A 5:45P
4:45P 12:15A Fargo, ND 5:00A 1:00P
10:45P 6:15A St. Paul, MN 11:15P 7:15A
4:45A 12:15P Milwaukee, WI 5:00P 1:00A
7:15A 2:45P Chicago, IL 3:15P 11:15P
Edit: I'm sorry that the schedule is formatted funny. When on the composition and edit screens, it appears spaced how I planned, but on the post, it is all centered to the left. Do the best you can with it.