If you drive 55 mph in a 55 mph zone, you can be given a speeding ticket:

California has a "Basic Speed Law," which means that you may never drive faster than would be safe in current conditions. Even if your speed is slower than the posted limit, you may still be cited if you are going too fast for conditions. When deciding how quickly to drive, drivers should take multiple factors into account, such as the speed of surrounding vehicles, the condition of the road surface, the presence of bicyclists and pedestrians, and weather conditions.