I went to court once for a traffic ticket that I got in a totally corrupt speed trap in I think like 1982. I took photos of the reduced speed sign blocked by a tree where the cops set up and had a whole defense setup. When it was my turn to go before the judge, I think I got to talk for like ten seconds before he stopped me and said "guilty as charged".
About six months later, a local attorney sued the city over the speed trap (which was an ongoing thing) and won. Too late for me, but at least others didn't get caught in the corrupt money making scheme by the city.
I think that is how some of the famous speed traps were shut down in Texas. Someone eventually sued or appealed the conviction high enough to get more notice. Plus, the state department of transportation adjusted the rules to make it harder for small towns to put stop lights or speed limit changes on state highways.