When the SD70ACes first came out, they did not have EMD's "Isolated" or "Whisper" cabs. Some crews claimed that the new units were louder (with their doors and windows closed) than SD40-2s (with their doors and windows open)! As a result, BNSF is ordering their newer units with Isolated cabs included. Note the "seam" that runs vertically on the sides of the cab just behind the nose. The cab is physically isolated from the rest of the unit, cushioning it and making for a quieter ride. This was the first SD70ACe that I had seen with the Isolated cab.
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