BNSF and US grain movement issues 'RRFN'

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If I have this right, a shuttle train is a unit train (110 cars?) designated to haul a commodity from designated point a to designated point b. usually applies to corn or beans as they are more generic in nature. Train cycles back and forth between points. purpose is to reduce turn around time. Haven't heard much about shuttles of wheat trains,maybe more common than I think.