[genocidicbunny]

That definitely takes up extra space. Notice all the room between the lanes. In many places in the US, you don't have even that. The intersection is literally only wide enough for two cars to go past each other, and _any_ amount of space taken up in the center means you need to widen the road.

[alistairSH]

Here's another one from Scotland. They don't have to take extra space. The version shown above only has extra space because they installed pedestrian islands - a nice touch but not required in many intersections.

Additionally, there is frequently extra space in the existing intersection. From parking lanes, shoulders, etc.

https://www.google.com/maps/@56.5902318,-3.3376212,3a,75y,34...

[genocidicbunny]

This is a much better example, thanks. That does indeed look like it doesn't really take up any more room -- the painted roundabout mostly seems to serve as a reminder of the yield order that people should take. In a way, its almost like a yield-controlled intersection here in the US. Those work relatively well as long as everyone follows the rules. In many places, this would just be inviting aggressive drivers to blow through intersections.

[alistairSH]

Exactly.

Worth noting this particular roundabout is in a small farming town on the edge of the highlands. Already slow speed road and low volume. But, shows that many 4-way stops within the US suburbs could easily be swapped with a roundabout during normal road repaving without much additional cost (yield signs to replace stops, some paint).