EPA's Tier 2 locomotive emissions standards that took effect in 2005. These Evolution Series locomotives are equipped with AC traction motors and are powered by a newly designed "GEVO-12" 12-cylinder engine that produces the same power as the 16 cylinder AC4400CW, but with fewer emissions and greater fuel economy. It also carries a redesigned air-to-air dual-fan heat exchanger, which gives it its distinct "oversized" radiator, a common spotting feature for these new locomotives. While the AC version has proven to be the overall most popular iteration of the "GEVO", quite a few railroads elected to use the DC versions of these engines, including the BNSF Railway, Canadian National, and CSX. THANKS FOR YOUR INTEREST IN OUR ITEMS.