It is illegal to place a container filled with human fecal matter on the side of any highway.

811.172 Improperly disposing of human waste; penalty.

(1) A person commits the offense of improperly disposing of human waste if the person is operating or riding in a motor vehicle and the person throws, puts or otherwise leaves a container of urine or other human waste on or beside the highway.

(2) The offense described in this section, improperly disposing of human waste, is a misdemeanor and is punishable by a maximum fine of $250.