The EMD SD70 is a series of diesel-electric locomotives produced by the US company Electro-Motive Diesel in response to the GE Dash 9-44CW. Production commenced in late 1992[1][page needed] and since then over 5,700 units have been produced; most of these are the SD70M and SD70MAC models. All locomotives of this series are hood units with C-C trucks, except the SD70ACe-P4 (and presumably the SD70MACH as well) which has a B1-1B wheel configuration, and the SD70ACe-BB, which has a B-B-B-B wheel arrangement. Superseding the HT-C truck, a new bolsterless radial HTCR truck was fitted to all EMD SD70s built 1992–2002; in 2003 the non-radial HTSC truck (basically the HTCR made less costly by removing radial components) was made standard on the SD70ACe and SD70M-2 models; the radial HTCR truck remained available as an option. All SD70ACe and SD70M-2 locomotives are, from the factory, equipped with one Nathan Airchime K5LLA-R1L airhorn mounted on a high-profile base. Due to height clearance restrictions, production models of the SD70ACe-T4 will be equipped with one K5LLA airhorn, mounted on a low-profile base, facing forward, and one "dual tone" K-13B airhorn, mounted over the rear headlight, facing rearward.
