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You are probably already aware of the library research guide for your class at http://library.uhd.edu/mba6212.

I suggest you use a resource called Statista. It had charts on both bus fares and Amtrak fares. See:

http://www.statista.com/statistics/187094/us-average-passenger-fares-in-intercity-rail-and-amtrak-since-1990/

http://www.statista.com/statistics/186768/us-average-passenger-fares-in-bus-traffic-since-1990/

If you want to look more at government statistics about transportation, see the site of the Bureau of Transportation Statistics at http://www.transtats.bts.gov/