i read an article in one of the car mags several years ago about how to fight a speeding ticked based on a rule the feds set on how states set speed limits. Basically the rule says they must set speed limits based on average speed of drivers on that section of road prior to limits being set. If the signs were posted without benefit of that study, they are posted unlawfully and cannot be enforced.
In other words, what Tony said. Drivers will drive at a safe speed regardless of signs. I did a cursory search to find that rule, but was unsuccessful. Wish I had saved the mag.
Another study showed that all the signs near intersections, actually caused accidents. When all signs near an intersection were removed, drivers behaved more carefully and accidents were reduced. The study was very small due to the difficulty of getting municipalities to allow the removal of the signs.
but it proved again that common sense will reign.
Unfortunately, the 10 to 15% of drivers who refuse to drive carefully will never bother using common sense. Like the corolla or other compact car who rides the bumper of my F250 thinking it will cause me to speed up!