625 ILCS 5/11-1408

No person or persons shall occupy a trailer, semitrailer, farm wagon, or any other vehicle while it is being towed upon a public highway, unless: (1) the occupancy of the towed vehicle is necessary to avoid an imminent threat to a person's safety due to extreme weather conditions or another emergency situation; (2) the speed of the vehicle does not exceed 15 miles per hour and the vehicle is used in connection with a parade, farming-related activity, or similar activity; or (3) the speed of the vehicle does not exceed 15 miles per hour and the passenger is over the age of 18.