California Code, Vehicle Code - VEH § 35707

Boards of supervisors in their respective counties may by ordinance reduce the permissible weights upon improved highways only which by reason of deterioration will be destroyed unless the weight limits are reduced, but no such reduction shall extend for a period of more than 90 days unless actual repair of the highway is begun within that time and thereafter continuously carried on to completion.

For the purposes of this section, an improved county highway means a highway paved with cement concrete or asphaltic concrete, or a highway with a roadway of hard surface not less than four inches thick made up of a mixture of rock, sand, or gravel bound together by an artificial binder other than natural soil.