Here in Ct if you do the speed limit you had better be in the right lane and watch your mirrors.
The average is 10 over the limit (65) and you still have a good chance of being run over. Generally I'm running at 72-85 and that will keep me pacing most traffic. There are many different types of unmarked state police cars here also. Dodge chargers, Tahoes, Explorers, Camaros, even Malibu's and smaller vehicles, in addition to the larger conventional Crown Vic and Suburban types. So spotting them is not always easy.
But.... If you see any vehicle on the side of the road with tinted windows or slightly open door, err on the side of caution and duck behind something BIG right away.