The article is more about what's safe on the roads and what prevailing traffic patterns bear out. It doesn't particularly encapsulate those with an uncomfortable past with law enforcement or those with a strategy. I don't go over 6mph over in areas I don't know unless I can find someone breaking the law. I will then give that guy 100 yards for every mph over the speed limit +6. Being the 2nd-fastest car on the road is just as fun as being the fastest and when the other guy is a half-mile ahead of you you're essentially speedtrap proof. Not only that, but most hot-heads can be goaded into breaking the speed limit even more than they would otherwise - especially if they're in a 2-door Japanese coupe or Volkswagen. Places I do know? Much more complicated codex of practices. Posted limits do figure into the equation, but are not necessarily observed.