It would have been better if your subject line focused on I80 past Chicago, as opposed to the full route.
The busiest part of I80 is where it runs with I94 through NW Indiana (Hammond, Gary). East of there I80 is the Indiana Tollway. I90 continues the tollway into Chicago. I80/94 is not only the through route EW, but also commuter route from this area into Chicago. But most of that traffic will turn north on I94 or I294. So imagine yourself a commuter working in Chicago or the NW suburbs, and avoid those times. Traffic will return to rural levels west of I55.