Idaho Code § 49-715: Riding on human-powered vehicles, bicycles, or electric-assisted bicycles.

(1) No operator or rider of a human-powered vehicle, bicycle, or electric-assisted bicycle shall ride other than on or astride an attached permanent and regular seat.

(2) No human-powered vehicle, bicycle, or electric-assisted bicycle shall be used to carry more persons at one (1) time than the number for which it is designed and equipped.

(3) An adult rider may carry a child securely attached to his person in a backpack or sling or in a child carrier attached to a human-powered vehicle, bicycle, or electric-assisted bicycle.