The subject of highway speed limits is interesting. When governments impose these limits, they do so with several considerations. First being safety. The way the road is designed...its geometry, the degree and superelevation of curves, the width of lanes, the clearance of fixed obstacles, the number and length of exit/entrance ramps, etc. Also, the degree of how well the road is maintained. And of course, the level of traffic at different times. Another is the users (drivers). What are the speed limits in proximity that drivers are experience in driving at. Mention was made earlier of how intensive the licensing of drivers is in Germany. They really have to prove their driving ability by entering and driving and exiting the autobahns at high speeds. Not just a ten minute road test consisting of a left turn, a right turn, a parallel park, and a 'U' or 'Y' turn, and then you're good to go, as we do here. I remember back in high school driver's ed, we asked the teacher when we would get on an expressway, and he looked shocked at the question, replying that we would learn that after we got our license! The German's have it pounded into them to keep to the right unless passing, and then to check carefully for faster traffic overtaking them before passing.
I once had the opportunity to drive the autobahn between Wiesbaden and Frankfurt in a Mercedes S320. Although it was only a '6', the big Benz had no trouble acceleration to 230kph. I passed about 70 percent of the traffic, but in turn was passed by Porche's and other faster cars. At that speed, in that superb car on that beautifully built and maintained highway, the ride was smooth as glass, and the car drove as if it was on a guideway. The last time I had driven anywhere near that fast was in 1972 on I-15 between Las Vegas and the Utah line. My 1972 Monte Carlo cruised along at 100mph all the way.
There is an axiom among traffic engineers that the safe speed of any highway is determined by the "85th percentile rule". That is the speed at which in light traffic, 85% of the vehicles are naturally travelling at or below. Any posted speed below that number is artificial, and will be disobeyed wide spread. The lower speed limit is imposed politically or purposely to raise revenue in the way of fines. Modern highways, and especially modern cars are designed to be safer than ever before.
Accident statistics show this to be true as annual traffic related death rates on highways per millions of vehicle miles has dropped signifcantly for years, even as speed limits have risen from those dark "double-nickle" (55 mph national limit) days.
