Amends the Illinois Vehicle Code. Provides that, on and after October 1, 2023, the default speed limit is 20 (instead of 30) miles per hour within an urban district, and 10 (instead of 15) miles per hour in an alley within an urban district. Provides that a county, municipality, or township with speed enforcement authority may only issue warnings for violations during the first 60 days after enactment. Effective immediately.