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Old 05-25-2011, 01:46 PM   #2
JRMDC
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From the Wiki:

http://en.wikipedia.org/wiki/EMD_SD70_series

"The SD70M-2 is a DC traction version of the SD70ACe, and the two models are nearly identical in every other respect."

You want to learn and understand the difference between AC and DC locomotives and why railroads pick one or the other. I think there was an article in Trains magazine in the last year or so. It may have even mentioned NS's recent change in what they buy. There may also have been press releases at various points in time.

BTW, often teachers require you not to rely on the Wiki, so find some good sources. When I am doing serious research the Wiki is a starting point, not a final source.

Also, investigate the impact of changes in EPA emissions regulation, look for information on various "Tier"s.
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