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Comment by wenc | Hacker News Reader

Yes. In theory, 4 way stops follow some simple rules -- whoever gets there first and makes a full stop goes first, and if more than one party makes a full stop at the same time, the party on the right goes first.

In practice we live in a world of (very illegal) rolling stops, people beckoning at each other to go first, people inching forward, etc.

That's not even considering some very stupidly designed four-way stops here in Illinois with two lanes on each side -- how the heck is one supposed to even figure these things out? It ends up being a game of chicken.

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Even the theory is not that clean cut.

What if two cars arrive simultaneously at opposite sides of the 4-way and are both turning left? This could easily deadlock two self-driving cars if not considered.

Your situation is a bit ambiguous. Do you mean they turn to their respective left (in that case their trajectories should not intersect), or to the same left? Not sure about USA, but where I am from the right of the way belongs to the driver who turns to the same side as the side of the road they are on, i.e. to his right (we drive on the right side).

Near where I live we've got two lanes + turn lanes on all 4 sides. It is a nightmare both as a driver and as a pedestrian. I'm not sure how that gets put in place or gets addressed as it inevitably gets busier. Traffic circles perhaps?

Traffic circles work better, but most people in North America have trouble with 2-lane traffic circles. (they're common in most places around the world)

Most people in north america have trouble with 1-lame traffic circles, because they're almost uniformly too small. Traffic engineers like to wedge them in as retrofits, when there's already a lot of stuff built up around an intersection, and it's not feasible to enlarge the intersection to make it work well.

Traffic signals with good sensors are more space efficient, and usually more time efficient when there's congestion, and more pedestrian friendly. Proper sensor design means no or little waiting during low traffic times too. Traffic circles can help with akward intersections though, where there's more than 4 entrances or exits, and some three way intersections work well too.

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