I drive a highway to work daily. One lane each way for the majority. I see this at least 2-3 times a week.
Odd thing is, it comes to a point where the road switches from one lane each way, to two lanes each way. The speed limit does NOT change. 60 MPH the entire way through. Drivers are NOTORIOUS for going 70 when there are passing lanes, and then shutting it down to 61 when it switches to one lane each way.
I've gotten to the point where I try to pass people when I can before it cuts down to one lane, but I inevitably get stuck behind someone who I simply cannot catch up to because they are also going 70 when I would've had the chance to pass.
In the end, when it is one lane each way, there is usually enough traffic to make it not worth the effort to pass. And it usually seems that there is enough traffic coming the opposite way that passing is difficult.
Any more I simply drive whatever speed the person in front of me is going and deal with it, so long as it is the speed limit. I tend to prefer setting the cruise at 65 (5 over), but there is no sense getting upset about driving 60.
Oh, and turns... gradual easy curves in the road... yep, better slow down and go 55 round those. That's simply too dangerous.