oh! that probably explains why i never in the almost 20 years here got tickets in such a situation, and i thought that i'm just good at spotting police cars (and slamming on the brakes each time i see a one) - here they are much easier to spot because they don't hide cheetah style in roadside bush like the traffic policemen do back in Russia.
Also in California "speed traps" are illegal: this is when a highway runs through a town or district and the district puts up a sudden "25 MPH" sign so they can catch out of towners and charge them money.
Adding too many lights and stop signs speeds traffic up rather than slowing it. Fortunately Cal. seems still (mostly) to hew to the "listen popular opinions to decide what to focus on; listen to actual domain experts to decide what action to take".
So the speed limit may be 25 but if the prevailing traffic indicates that everyone thinks 40 is OK then you can't get ticketed for keeping up with traffic.
I see this issue come up all the time in Palo Alto where I live: people want the speed limit enforced on, say, Embarcadero Rd, but if the the city were to do so they'd have to do a traffic survey which would actually tell them to raise the limit on the signs.
There was a wave of sensible lawmaking in California that was sadly abandoned in the Wilson+ era and has never come back.
+ I don't mean Wilson was the cause, though he was a bad one; he got elected in part because people forgot about being sensible in the regard.