During the day no officers have their radar set exactly on the speed limit as a matter of routine.
At Midnight, however, many drop their radar to the exact posted speed limit.
That establishes probable cause to stop anyone exceeding that speed, and trust me when I say that the hours between Midnight and 4 A.M. are "prime fishing hours." According to most estimates every third vehicle on the road between those hours on a Saturday or Sunday morning is being driven by someone who has been drinking.
So you stop a person for speeding, use your senses and experience to ascertain if they're drunk, high, or just heading home after the swing shift, and act accordingly. If he or she isn't loaded, you let them go with a warning to slow dowm.
In your example you state that you had a light burned out. That sounds far less a case of police harrassment than it sounds like you set yourself up to be stopped. You see, YOU don't decide what's a "public safety issue." Chapter 20 of the NCGS does that, and when you violate it the officer has a perfectly legitimate reason to stop you.
BTW, how in the world can an officer see you to judge your appearance when you're nothing more than approaching headlights on the opposite side of the highway?
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