625 ILCS 5/11-1408: Riding in towed vehicles.

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.