Some people feel safe at driving at 60 or more. But there is a point where regardless of the speed limit that we don't feel as in control of the car than we did when we were driving a few mph slower. That point is different for everyone.
I'm sorry, but anyone who doesn't feel safe driving at 60, in a modern car, in good conditions, on a reasonable road, shouldn't be driving. Are they going to still do 50 or 55 on a dual carriageway or motorway?
Our speed limit is lower than in many European countries. A lot of people, including senior police officers, feel that the limit on dual carriageways and motorways is too low. These speed limits were set when cars had shite brakes, no ABS, tyre technology was nowhere near as advanced, and no airbags or crumple zones. Stopping distance in a modern car is much less than in a Morris 1000, all other factors being equal.
I drive on rural roads almost every day. I don't generally get exasperated by slow drivers, I get that not everyone knows the roads as well as I do and there are a few places where the bends are deceptive (the classic diminishing radius bend can catch anyone out if they're unaware). I take account of the fact that they may be looking for a turning or the driveway to a house. I respect that they slow down for the bend with a school exit just beyond it, even if they slow down far more than I feel is necessary.
But I get royally pissed off by some drivers who I see regularly on one particular road, who do 40 for 5-6 miles on a 50mph road, find it necessary to brake every time a car comes the other way, slow right down for even the gentlest bend and cannot, simply cannot, overtake a cyclist, even when they can see 200 yards ahead.
And if you are the 30-ish woman driving a black Ford Kuga in East Sussex between 9.20 and 9.40 on weekday mornings during termtime, I mean you! But you're not the only one.