For a changed prima facie speed limit, the key words here are, the same shall be applicable unless . . . . Giving these words their plain meaning one can only conclude that for such a speed limit to be valid, it must be both authorized in the Vehicle Code and posted on signs. But most importantly, the statute making the offense a crime is intimately connected and fully conditioned upon compliance with, the statutes that establish the speed limit. The criminal statute is worded in such a way that if the speed limit isn't valid, then it's no crime to ignore it. Simply put, without compliance with the stated requirements by the persons who established the changed speed limit, one does not commit a crime in violation of 22352.
Examples are plentiful.
Speeding detentions often occur on city streets in areas where a traffic and engineering survey has authorized setting a prima facie speed limit above the 25 m.p.h. limit set forth in 22352. That statute also requires an engineering and traffic survey that justifies the new speed limit, along with posting. Therefore, since 22351 conditions the criminal offense on a speed limit complying with 22352, and that statute authorizes a change only when authorized in this code , proof of the criminal offense requires proof of the survey, and proof of posting. If the required engineering and traffic survey justifies a 65 m.p.h. speed, but the speed limit is set at 60, it's invalid and unenforceable. In short, the speed laws are filled with requirements that must be met in order for the various speed limits to be valid and enforceable as criminal prohibitions.