Anyway, the roundabout result was interesting, but I still don't quite understand how they work. I mean, how do you decide whether to go forward or to stop and let another car move ahead of you? How do the accident rates compare?
Rundabouts are simple, just remember that cars in the rundabout generally has precedence. Then it's just a matter of judgement of if you can go before any car already in it, say if there is a car at the opposite side of you or if they are signaling that they are exiting. Signaling that you are exiting is very important because that will tell those who wants to enter that there is space to enter the roundabout.
I'd say the biggest advantage of a roundabout is that you as a driver only have to care about cars coming from the left, compared to any other fourway intersection where you have to be observant of three.