It shall be the duty of each rider to heed all posted and oral warnings and to refrain from acting in a manner which may knowingly cause or contribute to the injury of himself or others or in a manner contrary to prohibited acts for riders set forth in section 3 . Notice of these prohibited acts shall be displayed as set forth insection 5 . Proof that a rider sustained an injury in the course of knowingly acting contrary tosection 3 shall be evidence of comparative negligence in a suit against an operator by that rider.
4 P.S. § 504