As the person who is usually the one zooming up the roundabout, the people who misjudge my speed annoy the **** out of me. In general I'm not speeding as such (it's all but impossible to take most roundabout at much more than the local limit), but I'm doing it faster than most people do it, and the number of people who think it's safe to pull out in front of me when it really isn't is astonishing - it probably happens at one roundabout in three.
I have a theory, which goes like this: most drivers don't actually estimate the speed of the oncoming driver, but instead judge the distance, and assume that the oncoming driver will take the roundabout at the speed that the judging driver would, if it was them (if you see what I mean). Thus Mr Slow, seeing an oncoming car, assumes that it will take the roundabout at 15mph, because that's how they in person drive. Except I don't: I've got AWD and I intend to use it, and that roundabout is going down at 30mph - even is a little drifting might happen.
M