https://www.youtube.com/watch?...amp;feature=youtu.be
By pure luck I caught one of the Tier 4 test beds on the Atlanta to LA stack train as it was coming through Dalton GA. I quickly gave chase up to Warring road for another shot of it.
These demos are somewhat different from production Tier 4 units as they have a larger "hump" in the center and a horn located (almost hidden) in the radiator section of the engine.
Also, unlike production Tier 4's, these test units were still called ES44AC's, where as the production units are called ET44AC's with the T standing for "Technology".
Enjoy!