That's exactly the issue. You should not be surprised when you are hassled. Currently, you can be pulled over for doing 59 in a 55. As far as I can tell nobody does 55, unless it is in a 45. You shouldn't have to guess what is acceptable in each county or town. You should know what the real speed limit is.

Is there a 4 mph "forgiveness" in the law somewhere? I thought that technically it was an infraction to travel 56 in a 55, which is equally ridiculous as being ticketed for going 59 in the same spot.

I own a car that encourages the driver to go fast (think Autobahn speeds) with its power and ride comfort. I am still going slower than 60 in the 55 zones.