Section 41100 Of Chapter 4. Presumptions From California Vehicle Code >> Division 17. >> Chapter 4.

. In any action involving the question of unlawful speed of a vehicle upon a highway which has been signposted with speed restriction signs of a type complying with the requirements of this code, it shall be presumed that existing facts authorize the erection of the signs and that the prima facie speed limit on the highway is the limit stated on the signs. This presumption may be rebutted.