The EMD F40PH is synonymous with the Amtrak era of American passenger trains. Although it has been retired from Amtrak service, it operated for over 20 years and today it continues to be the motive power for commuter railroads such as VRE, MBTA, Caltrain, Metrolink, and Metra) and more all over the United States. Over 400 F40PH locomotives have been manufactured by EMD in various configurations.

To support passenger service, the F40PH is equipped with a secondary electrical generator referred to as the head end generator (or HEP, for Head End Power). The need for constant constant frequency power means that these HEP units are constantly running at 900rpm, resulting in the nickname “Screamers” for the units due to the sound.