Railroad overpasses are so ubiquitous that they tend to get ignored. This crossing is not one of the longest "urban tunnels" in Chicago by any means, but it is interesting because you can still discern their original signs.
Andrew Urbanski posted four photos with the comment: "Interesting find on 79th street, just east of CSX’s Forest Hill Yard. The bridge is still marked Baltimore and Ohio / PENNSYLVANIA RR."
Normally, it would be two separate bridges that happen to be very close to each other. The following street view shows that it is two separate bridges. The 2-track span that still covered with yellow paint was the Pennsy and the 4-track span is CSX/B&OCT. Notice the webbing on the girders is different. It may be that the railroads hired the same contractor to build both. That would explain why details like the embankment linings look the same.
(I'm really impressed by the exposure the street-view car got. I've tried taking photos of underpasses, and they can be rather dark.)