> Presumably the place where people are speeding the most is where it's most dangerous.

This is so stupid I don't know what to say.

No, speeding in an area where traffic flows smoothly and evenly and where no pedestrians or bikers are ever present is not more dangerous than speeding in a school zone where kids are walking home. Yet far, far more people will exceed the limit dramatically on the highway, especially when limits are set artificially low.

Speed is not in itself dangerous. Speed differential is. The most dangerous situations are where you have things moving fast next to things moving slow. Things moving fast next to things moving fast is actually quite safe.