Wyo. Stat. § 31-5-119: Clinging to vehicles.

(a) No person riding upon any bicycle, electric bicycle, coaster, roller skates, sled or toy vehicle shall attach it or himself to any vehicle upon a roadway.

(b) This section does not prohibit attaching a bicycle trailer or bicycle semitrailer to a bicycle or electric bicycle if the trailer or semitrailer was designed for the attachment.

(c) No person operating a vehicle shall permit a passenger to ride on the fender or running board of the vehicle nor shall any passenger ride on the fender or running board of a vehicle. This subsection does not apply to a commercial vehicle or a vehicle operated by or for a political subdivision of this state designed to permit a passenger to ride on a fender or running board, such as a fire department or trash collection truck.