It's my opinion that people will always try to exceed whatever limits are set. It's human nature.

This is not correct.

Many different studies (here is just the first one Google brought up) have demonstrated time and time again that the "85th percentile rule" is ubiquitous. In summary, the speed that about 85% of the drivers employ (+/- 5%), even in an unregulated enviornment, is the optimum speed for any particular road in terms of both traffic flow and safety. In other words, the great majority (like about 85% ) employ reasonable speeds regardless of the posted limits.

Speed does not kill. It's speed differential that is dangerous. Somebody driving at the legal 55 MPH speed limit when 85% of the traffic is moving 15--20 MPH faster is far more likely to cause an accident than the person driving illegally at 80 MPH.

tanstaafl.