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Comment by buro9 | Hacker News Reader

Swindon, UK would like to remind the World that recursive roundabouts are a thing too.

https://i.imgur.com/4pMhdMl.gif

How is that a thing? Why not just have a two-lane roundabout with the third lane skipping the roundabout and going to the next exit directly?

According to this video[0], it reduces the fight for space. IIUC, the idea is that this structure allows the flow to avoid the pile ups because you have more than one way to do something and if the one way is too busy you can take the other.

Imagine a single roundabout with large number of lanes that can go just one way or exit the roundabout, then you can easily have a pile up in one exit block the drivers haded to the other exists. However, if the roundabout can go both directions the drivers can go through the other side of the centre.

[0] https://www.youtube.com/watch?v=6OGvj7GZSIo

I don't know, those images of cars standing still on the roundabout are not very convincing that this is an efficient way to do it. I'd love to see this compared to the more structured Dutch turbo-roundabouts: before you enter the roundabout, you pick the lane for your exit, and you just follow that. You only cross other traffic once, on entering the roundabout. After that, it's smooth sailing to your exit.

We have another one which is just as cool. https://imgur.com/WfFXmBg https://imgur.com/IFIZI2q

They actually work really well.

I'd love to see some of the things that generative ML could do in this space :)

The recursive design allows you to go the "wrong" way around the "big" roundabout.If you want to take the exit immediately to your right, the "single huge roundabout" design would require you to go almost all the way around to reach your exit. The recursive design allows you to take the third exit from the first two mini roundabout. Sorry if that's unclear, it's a bit tricky to explain in words.

Another advantage of the recursive design over a big roundabout is that it keeps traffic speeds slow, so collisions are much less deadly.

The video embedded near the end of the article also shows this particular roundabout.

I'm not surprised that pedestrians are waiting to cross rather than taking right of way at an abomination like that. With driver load that high it would be suicidal, whether or not they legally have right of way.

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