Commuters from the city going back to their homes can jam up on I-80, although it shouldn’t be too bad if you’re there on a weekend or during the day before 5 pm or after 9 am. There’s no true way to bypass I-80 going through Chicago, so riding it out is the best plan if there’s congestion or construction.
I-80 through Illinois covers approximately 175 miles, taking about 2 hours and 45 minutes to drive. It runs mostly through farm country, so you won’t have a ton to see on the way. If you want to take a break midway, Starved Rock State Park has Louis Canyon Falls, which you won’t believe is in Illinois until you see it.