The EMD SD70 is a series of diesel-electric locomotives produced by Electro-Motive Diesel in response to the GE Dash 9-44CW. Production commenced in late 1992[page needed] and since then over 4,000 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.
Prior to the SD70ACe and SD70M-2 models, all SD70 models were delivered with the self-steering HTCR radial truck.[note 1] The radial truck allows the axles to steer in curves which reduces wear on the wheels and railhead. With the introduction of the SD70ACe and SD70M-2 models, EMD introduced a new bolsterless non-radial HTSC truck as the standard truck for these models in an effort to reduce costs. The HTCR-4 radial truck is still 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.