The 101 through Sonoma/Humboldt/Mendocino counties is, at some places, a 2-lane highway weaving its way through a twisty curvy Redwood forest at 55-65mph, and up to 75mph when it's a six-lane highway. And here in Southern California I regularly get away with 80-85mph in front of CA highway patrol. Most places I've been to in the US seem to consider 5-10 over the limit to be acceptable. I have even heard of freeways in Texas permitting 80 MPH! So these speeds are not unheard of (maybe on a country road but you'd expect the kind of treatment that guy got for 100MPH+)
Judging by your writing you sound British, IMO speed limits in a lot of Europe are ridiculously low; our highway speeds shown in MPH are often a larger number than your highway speeds shown in KPH.
