Forget about studying the "new math" in school. All you need to do is get in your car, find the nearest highway, set your cruise control at the set speed limit... and watch.
It seems that there is a special formula that applies to speed limit calculations. When the sign says "55," most drivers go 65+. When the sign says "65," the standard speed is 70-75. And when the sign says "70," the standard speed is 75-80+.
And this is not limited to highway driving. Try doing the posted 30 miles per hour in a residential area and watch the blood pressure levels of the drivers around you rise.
What is it with people that they simply cannot obey the speed limits? I do not buy the argument that people feel that they can drive safely at a higher speed. Even if that is true, it does not account for the consistent levels of "pushing the envelope" of speed. If there were a posted speed limit of "80", people would do 85-90 as the standard. I think it is simply a matter of drivers getting away with something they are not supposed to do... kind of like sinning without the religious and spiritual consequences.
In my opinion, the government should either enforce existing laws or do away with speed limits altogether. The existing system is a joke. It gives law enforcement a tool to harass drivers on an individual basis and only serves to encourage disrespect for law enforcement.
Besides, leaving the situation the way it exists is simply too dangerous for those of us who try to observe posted speed limits. Although there is a raging debate over whether higher speeds lead to an increase in traffic fatalities, it is clear to me, through personal observation over the years, that the people who speed either get into accidents or cause other people to have accidents due to their carelessness.
If we want to have a "free-for-all" on the roadways, so be it. At least we will know what to expect when we get in our cars. However, when you get into your car, you have an expectation that others will be observing the same rules you are. When that does not happen, anything can happen on the roadways... and it does, on a regular basis.