Illinois Routes 190, 194, and 594
Lengths: IL 194 was 19.5 miles long, IL 594 was around 2.3 miles long, and IL 190 was 30 miles long.
Termini: IL 194 went from I-94 near the Loop to I-290/IL 53 (when I-290 was I-90). IL 594 went from IL 194 (now I-90) to O'Hare International Airport. IL 190 started at the I-290 (then I-90)/I-294 junction and went westward to US 30 north of Aurora.
Reason for decomissioning: After seeing it more logical, I-90 was routed on IL 194; this made IL 594 into I-190. IL 190 had been decomissioned years before and was just IL 5.
History: IL 194 was to have been I-194, according to Kurumi's Chicago page. It comprised of the Northwest Tollway and the Kennedy Expressway. IL 194 originally followed the JFK Expy. to O'Hare; the spur later became IL 594. That changed when I-90 was rerouted on IL 194's route for continuity.
IL 190 was once the East-West Tollway. But before the 1970s, it was renumbered to IL 56. It eventually became I-88 because Illinois wanted the East-West Tollway to have 65 MPH as its speed limit. IMO that is a waste of Interstate designation...BUT it could become a good way to fix the Quad Cities Interstate confusion.
I-88 could take over I-80 from I-80/280 split to I-88/80 split. I-80 from I-88 south to I-280/80/74 would be I-480. I-80 would be on I-280's current path. Simple, eh?