Railfanning Union Pacific

[Herc Driver]

Thanks guys! I get to the LA area quite often, actually, there's not too many places I don't go in the US so there's a chance that I can make and see one of these DD-units in person. What always amazes me is the technical decisions that were made prior to any metal being riveted together. Why did the UP officials require the power of the DD units, what economic benefits made the purchase and production viable, and why were they taken off the roster. Sure they're amazing looking units, but there's always an interesting story to the how and why something like this is made.