I talked to H about what we were talking about in the UO. This is a summary of what he said.
Yes, he responds to more accidents on regular, non-highways than on highways. Furthermore, the non-highway accidents are, statistically speaking, more lethal. This is because highways are designed to be safe. Everything, from how you merge, to how wide the median between opposing sides of traffic are, is regulated and designed to be as safe as possible. Accidents are almost never head on collisions. Unless someone is driving drunk, you're much safer on a highway than on a side road. Side roads are not designed to be safe. They have people turning randomly, stop signs all over the place, and traffic coming at each other head-on. This is why most accidents happen on side roads.
As far as fatalities dropping in the US, it is entirely a result of cars becoming safer. Higher safer standards means that when a (newer) car is in an accident it crumples around the passengers in such a way as to protect them.
My H also has a question for you Dorothy Zbornak. He says he heard somewhere that in Germany, when you get a traffic ticket you are not fined a set amount but a % of your income. Is this true?