625 ILCS 5/11-1505.1

Persons riding bicycles or motorized pedal cycles upon a roadway shall not ride more than 2 abreast, except on paths or parts of roadways set aside for their exclusive use. Persons riding 2 abreast shall not impede the normal and reasonable movement of traffic and, on a laned roadway, shall ride within a single lane subject to the provisions of Section 11-1505.