This pic, shows a 30 y/o round-about, at the circle road of my 50k town. South east leading to industrial area, north east to town. North is the circle, west it to the next town.
In small sub-urban "traffic-circles" you would have pedestrians (or god forbid, bike-commuters) going around the edge. That obviously doesn't work at all for heavy traffic or freight. That would be madness. But it would be equally stupid to just believe, that there's no way one could think up a solution - we need to keep the traffic lights, and the road accidents it has. This design has a very long turning radious, meaning it's easi to navigate for large trucks. This would have been really dageroues from the bike commuters, those bike lanes are regional ones. The one going left has 10km to the next village, and 30k to next town. And yes, they're used, and not some new progressive path - been there all my life, i'm 30. the solution is simple, navigate the traffic beneath the round-about with a junction in the middle. In this case, it's for the bikes alone, so they created a bike round-about in it. This works fantasticly.
You know how it's claimed they reduce traffic accidents in general? Mostly, the reason they're annoying is the reason they're safe - you have to slow down, and look around. Instead of continuing like a zombie. But this one case shows another reason. When they're constructed right, with land in the middle to stop vehicles, speeding idiots at night, will go intro the trap, and stay there as the fools they are. See how there's missing trees in the north and south east directions? Yeah, drunktards speeding right through the trees. We have those to sadly. Now, during the night, there's luckily few bikes if any in the middle. But there would be cars on the road still. So chance are, that had there been a traffic light, those speeding idiots would have side hit other cars - as i hear so often happen in the US.