IL SB3501

Establishes 70 mph speed limit on interstate highways outside Cook, DuPage, Kane, Lake, McHenry, and Will counties, with 65 mph on designated 4-lane divided highways and 55 mph on all other roads in those areas.

Maintains existing speed limits in Cook, DuPage, Kane, Lake, McHenry, and Will counties (65 mph on toll highways and designated highways, 55 mph on other roads).

Permits the Department of Transportation and Illinois State Toll Highway Authority to set speed limits up to the new maximums (rather than the previous 65 mph cap) based on engineering and traffic investigations.

Keeps urban district speed limits at 30 mph and alley speeds at 15 mph statewide.

Applies to passenger vehicles, with separate provisions maintained for buses and heavy trucks.