[mdpye]

A mini-roundabout is a centre circle painted (not curbed), plus the priority rules (give way to your right - would be your left in the US).

They don't take up any extra space, but they do probably require drivers to intuitively understand the concept and priorities before they can be introduced.

Here's a satellite view of a random one near me: https://goo.gl/maps/NJ2KpYdMP1reQA1u5

Its an upgrade of the American 4-way-stop with better defined priorities for entry.

[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).

[cogman10]

Yeah... I don't think those will work in the US until roundabouts are a lot more common.

The issue I've seen with them in the US is many US drivers ignore pretty much everything about the painted circle which creates a really dangerous situation. They treat those intersections like 4 way stops (including driving over the circle) and that's a major problem.

[drewzero1]

Not to mention that in large areas of the northern US, any painted road markings are likely to be covered by snow and ice a good portion of the year.

[rascul]

You're still supposed to drive around the circle though, right? Or am I misunderstanding?

That intersection you showed is clearly big enough. This one doesn't look big enough. Or is it? There are smaller intersections than this one, also. (And I realized that this one might be a bad example because it's not four directions.)

https://goo.gl/maps/fBEysywZgdQVWH7N9

[alistairSH]

At some intersections in the UK, the roundabout is literally a small circle of paint. The car doesn't really go "around" it because it's so small. It mostly exists as a visual cue that the intersection follows roundabout rules.

[rascul]

Ok, I was working under the impression that one must drive around the circle. If that requirement isn't there and it just changes how we work out who goes when then I can see that expansion wouldn't be necessary.

[ben_w]

The north and south exits to the roundabout are 10.5m across, including the traffic islands; the west exit is 5m across. The 4-way junction you've linked to, the exits are 9.5-11 meters across.