Comment by peeters | Hacker News Reader

Comment by peeters | Hacker News Reader

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Not sure exactly what you mean by freely, but in most popular roundabout designs you can exit from the inner lane. A "standard" two lane roundabout will have two lanes entering AND exiting. You never change lanes in roundabouts, at least where I'm from. Only in a massive multi-lane roundabout (that's at that point more like a ring road) would you ever change lanes to exit.

e.g. for a standard two lane roundabout with four exits, if you enter in the left lane, you can exit directly out of the 2nd, 3rd, and 4th (i.e u-turn) exits, but always in the left lane of the exit. If you enter in the right lane, you can exit out of the 1st or 2nd exits, but always in the right lane of the exits. With this design cars travelling alongside you can never cross your path, only cars entering the roundabout ahead of you can cross your path and it's their responsibility to yield.

The thing that most often causes problems is people in the outer lane NOT exiting (e.g. thinking they can take the third exit from the right lane) and swiping the car in the inner lane correctly taking the second exit.

The car from the inner lane swiping into the car in the outer lane is the exact issue I'm talking about. The problem is when drivers enter in the left/inner lane, fully intending to take the first exit. If they proceed to exit directly from the inner lane, without first changing lanes, signalling, or yielding to outer traffic, they would intersect with a car in the outer lane innocently heading to the second exit.

In practice, people are not able to navigate two-lane roundabouts in a compliant and safe manner. Any intersection of roads busy enough to have two lanes in each direction is too busy for a roundabout to be safe.

It’s still safer than a normal intersection. Roundabouts prevent HIGH SPEED t-bone and head-on collisions. The difference in safety is easily worth the “cognitive load” of a 2-lane roundabout.

I think drivers will get used to them and in practice there will be few collisions.

> I think drivers will get used to them and in practice there will be few collisions.

I think drivers will avoid them at all costs since even low speed collisions can cause extremely expensive repairs (and even total an older vehicle) meaning they'll never get the practice they need to navigate them safely, yet eventually those drivers will find themselves in a situation where a roundabout can't be avoided and suddenly it's chaos for every car in the intersection.

Even if multi-lane roundabouts were suddenly everywhere we'd probably need generations of new drivers trained to use them in drivers ed classes as teens before you could just trust people to be able to navigate them correctly

The experience of most NZ cities and towns on a daily basis says otherwise.

> The problem is when drivers enter in the left/inner lane, fully intending to take the first exit. If they proceed to exit directly from the inner lane, without first changing lanes, signalling, or yielding to outer traffic

Yes, in that case a driver not understanding the rules of the road (that you can't take the first exit from the inner lane, which is usually clearly signed) could cause an accident. The exact same way turning right from the left lane in a signalized intersection can cause an accident. The question is, what's the damage of an ignorant driver and how fast do people learn? The research indicates that right-of-way incursions in a roundabout result in dramatically fewer injuries than right-of-way incursions at other types of intersections, and the research also indicates that contrary to your belief, drivers actually do learn how to use them.

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