Which Speed limits don't really do much and do more to generate ticket revenue than they do to save people, or that people drive at speeds they're comfortable driving at?
Nationwide, when the speed limits were raised on interstate highways from 55, the rate of accident fatalities didn't go up by some astronomical amount, in fact they continued a downward trend, the same trend that continues today. Improved car safety, improved road upkeep, more national awareness about the dangers of drunk driving and things like that keep roads safer, speed limits that no one follows play a much smaller role in that than many people think.
On the other hand, there are entire towns that AAA warns people to avoid because they're notorious speed traps. A few of them are here in Florida, in Starke, Haines City, and Waldo. These towns, and a lot of other ones, have arbitrary reductions in speed on roads that are perfectly safe to travel at the previous speeds mentioned that are hard to notice, and result in a huge amount of money for their town in the form of fines. And we're not talking about a 5 mph reduction so they can nab people who were already speeding, I'm talking about 20+mph reductions, from 55 to 30, and 65 to 40, with police stationed at these points essentially 24/7 with a radar gun to catch people moving through.
I've seen it happen with my own eyes, and have had friends nailed by it. Speed traps are so bad, and so notorious that there are entire websites dedicated to informing people about it.