Switching activity at the Belt Railway of Chicago, Clearing Yard. Chicago / Bedford Park Illinois USA. July 2007.

I took this photo after work one hot summer afternoon, in July of 2007. We are looking east from the South Cicero Avenue overpass bridge near West 67th Street. Seen here on the "East" or "Chicago" side of the South Cicero Avenue overpass bridge, are a Belt Railway of Chicago large EMD roadswitcher and a trailing non powered ( No prime mover /Engine block) Slug Unit for heavy switching duty. Slug units are usually rebuilt from components of retired or scrapped diesel locomotives.
The slug unit gets electrical power to the traction motors on the trucks, from the diesel roadswitcher coupled to it via electrical cables. Only the trucks are powered, while the carbody above the frame, is ballasted for weight and traction.