There is a simple roundabout I have to drive through every day arriving and and leaving work. All of us here at work call it the circle of death. Almost daily I see people driving the wrong way through it, stopping in the circle to let approaching traffic in instead of the other way around, or some asshole blazing into it and crashing into somebody else who had the right of way. There are several accidents in it per month. My only rule with it is not to get hit. Navigating it when it is busy ALWAYS ramps up my heart rate. I've actually gotten in the habbit of using the horn while on the motorcycle just to make damn sure people are watching me while I go through and I don't get plowed into by somebody blazing into it at 30 MPH. I think the biggest problem with this circle is that it is divided into two lanes, but it is on the small side for this. There isn't time to change lanes before you need to exit the circle again, so the lanes are essentially meaningless and people just dive into and out of whatever lane they feel like. The other problem is that this circle is heavily trafficed by folks going into and leaving the state's biggest public university hospital. This means that they A) are old and can't drive, B) are illegal immigrants and don't give a shit, C) have never been here before and have no idea where they are going and how to navigate the circle, or D) all of the above. Lastly this roundabout has crosswalks at every entrance and there is a ton of pedestrian and bicycle traffic due to being a college campus. Mix this all together and you have a nightmare. There is another roundabout on the other side of town that is roughly three times the diameter of the one I was just discussing, and it is generally only trafficked by people who know about it, and it runs VERY smoothly. There are also several in Payson AZ, which I visit a few times a year since my dad lives shortly north of there, and those all work really well too. In short, I like them when they work, and the people driving through them understand them. But make them too small, and in an area crowded with drivers who have no idea what's going on, and they are disaster zones.