I've lived in the US all my life, with my excessive number of years split between Michigan, North Carolina, and northern and southern California, and in all of

I've lived in the US all my life, with my excessive number of years split between Michigan, North Carolina, and northern and southern California, and in all of those places the proper range of speeds was anywhere from the posted speed limit to a hair under 10 MPH over the posted speed limit (I prefer the latter :). Go slower than that and you start blocking traffic, go faster than that and you might get a ticket. This is when driving on highways and major roads, at least. I vividly remember the days of 55 MPH speed limits in the US, and it was pretty much the same then (a hair under 10 over was the optimal speed, but 10 over was a lower speed back then). Anecdotal experience and all, but at least for me and other drivers that I've observed or talked to about it, just because people tend to go over the limit doesn't mean that the limit has no effect. This is all fine by me. I only mention it because this is exactly the kind of topic overly logical people (and/or inexperienced drivers) tend to get bent out of shape about. Just because the speed limit isn't strictly enforced doesn't mean it's useless, and just because a cop could theoretically take advantage of people's behavior and give a bunch of tickets to people for going 5 over doesn't mean that it's a conspiracy by the police.