Safety benefits of roundabouts • Hacker News Board

Re: Safety benefits of roundabouts

#71

Post by stvltvs » Wed, Oct 25, 2023, 8:50 PM UTC

a_e_k wrote: post #50

Personally, I'm fine with the simple single-lane roundabouts. They're convenient for U-turns, for example. For anything above that where I have to cross lanes to get to the center circle and then cross lanes again to get back out and exit, I'd rather just have a conventional traffic light-controlled intersection. (I try to minimize lane changes when I drive.)

> I try to minimize lane changes when I drive.

Same here, but by the end of a recent trip to Iceland, two lane roundabouts were easy-peasy. The learning curve is short in my experience.

Re: Safety benefits of roundabouts

#72

Post by boricj » Wed, Oct 25, 2023, 8:51 PM UTC

hristov wrote: post #20

The greatest thing about roundabouts is that they protect against the idiot that goes through an intersection at full speed. He does that either because he is passed out behind the wheel or because he did not notice a stop sign and thought he had the right of way, or maybe because he just does not care. Well with a roundabout if you just go straight ahead you hit the center circle. Good roundabouts always have a slig…

Not necessarily. Some roundabouts have the center circle partially paved so that oversize loads can drive right through if needed. There are curbs, speed bumps and road pillars that make it obvious for normal traffic not to take the shortcut.

It also doesn't fully protect vehicles already inside the roundabout. My father got rear-ended once while inside a roundabout by a possibly distracted driver and the car was a near write-off.

The main advantage of roundabouts is traffic fluidity. When compared to intersections with stop signs or traffic lights, unless it is full you can often enter a roundabout without coming to a complete stop first.

Re: Safety benefits of roundabouts

#73

Post by m463 » Wed, Oct 25, 2023, 8:52 PM UTC

throw0101a wrote: post #65

_zamorano_ wrote: post #53

In Spain we use roundabouts heavily. They're perfect for crossings with low to middle traffic. No useless waiting time, good visiblity and no need for traffic lights. For heavy traffic, though, they're useless as the car flow of one entry/exit can take over the roundabout and block all other entries. Also, it seems hard to understand for many drivers that regulations regarding changing lanes don't change in a roundab…

> For heavy traffic, though, they're useless as the car flow of one entry/exit can take over the roundabout and block all other entries. Not wrong, but traffic lights can be added to roundabouts as well ("signalized roundabouts") * https://www.youtube.com/watch?v=XCrAPcUzOdw So if an intersection is (e.g.) four-way, and one particular entrance monopolizes things than it can be given red at times and the others green…

wow this stuff is like factorio, where you learn signals.

too bad you can't go underground.

Re: Safety benefits of roundabouts

#74

Post by throw0101a » Wed, Oct 25, 2023, 8:58 PM UTC

devnull3 wrote: post #68

Simple roundabouts are definitely good but in UK I have found spiral roundabouts error prone if you have not driven on it before Example: [1] When visiting for the first time on a specific spiral roundabout: 1. Lane markings are faded 2. You do not know the specific lane unless you come very close to it and have to make a quick decision 3. Often due to queued traffic you cannot even see the lane marking until its too…

"Spiral Roundabouts | Understanding what to do":

* https://www.youtube.com/watch?v=e6TsX9Ob91w

I'm more curious about the straight-through path of [1] above.

Re: Safety benefits of roundabouts

#75

Post by Minor49er » Wed, Oct 25, 2023, 9:01 PM UTC

peterpost2 wrote: post #40

Minor49er wrote: post #4

Earlier quoted context omitted.

As an American, I can assure you that we have loads of these

France has about 30k of them, the UK has about 25k of them and those countries have a fraction of the population of the US. The us does not have loads of them they are few and far between

"Fewer than what's in France and the UK" is an interesting metric. Apparently it doesn't matter that there are so many that the only way to get through certain parts of various cities in most states is to drive through multiple roundabouts in serial. That certainly qualifies as "few and far between" simply because there are fewer than what's in France

Re: Safety benefits of roundabouts

#76

Post by gniv » Wed, Oct 25, 2023, 9:02 PM UTC

gnicholas wrote: post #17

Interesting that there are no listed downsides. I saw a more balanced article a while back and recall that it listed cost (especially of the additional real estate, since roundabouts are larger) as being one downside. And in built-up cities, it's basically impossible to convert traditional intersections to roundabouts, because there's simply no room. It is nice to not have to pay for replacement signals, or have to d…

Another downside I'm noticing: During rush hour you wait a lot if you're turning into a busy road.

Re: Safety benefits of roundabouts

#77

Post by foobarian » Wed, Oct 25, 2023, 9:02 PM UTC

sokoloff wrote: post #21

squarefoot wrote: post #8

Safety aside, roundabouts lower traffic significantly by never forcing cars to stop. Congestion increases as cars need to stop because of the inevitable latency propagating along the tails, and having more than one traditional intersections along the way can only make things even worse, so any solution to prevent cars from slowing down to a stop would mitigate those effects.

Until you do what Cambridge, MA has done twice near my house: put a traffic light just outside the roundabout, so when the light turns red, traffic inevitably backs up through the roundabout, locking it up entirely. https://www.google.com/maps/@42.3875777,-71.1422076,18z?entr...

The circles of death? :-)

Re: Safety benefits of roundabouts

#78

Post by devnull3 » Wed, Oct 25, 2023, 9:08 PM UTC

throw0101a wrote: post #74

devnull3 wrote: post #68

Simple roundabouts are definitely good but in UK I have found spiral roundabouts error prone if you have not driven on it before Example: [1] When visiting for the first time on a specific spiral roundabout: 1. Lane markings are faded 2. You do not know the specific lane unless you come very close to it and have to make a quick decision 3. Often due to queued traffic you cannot even see the lane marking until its too…

"Spiral Roundabouts | Understanding what to do": * https://www.youtube.com/watch?v=e6TsX9Ob91w I'm more curious about the straight-through path of [1] above.

There is a sign board which tells whether to take the middle road or left [1]

This is the round-about layout [2]

None of the above tell the precise lane to take. Only when you enter the roundabout you will know. See.[3]. Imagine cars waiting on these markings. This is what frustrates me the most.

[1] https://www.google.com/maps/@51.5066257,-0.5789164,3a,75y,32...

[2] https://www.google.com/maps/@51.506316,-0.5784722,3a,37.5y,2...

[3] https://www.google.com/maps/@51.5076664,-0.5804344,3a,75y,29...

Re: Safety benefits of roundabouts

#79

Post by smegsicle » Wed, Oct 25, 2023, 9:08 PM UTC

sokoloff wrote: post #66

smegsicle wrote: post #64

Earlier quoted context omitted.

note that proper spinlock procedure is to not leave the roundabout unless there is room to do so completely this avoids complete deadlock until the entire roundabout is full of drivers who refuse to take any unblocked exit, while continually offering each the ability to do so

> not leave the roundabout unless there is room to do so completely I don't understand how that helps. The problem is there are too many cars in the rotary, so no amount of not leaving the rotary will unblock it. It seems like you should not enter unless there's room to exit, but on some of these, you can't both see the exiting traffic light and safely merge into moving rotary traffic, so I don't really blame drivers…

as an ai language model, i cannot speak to your particular intersection, but the idea is that if say just one car is waiting for the blocked exit, circling would allow other exits to continue to function, by following the general rule of 'do not stop once entering the roundabout'

i could also imagine that anyone waiting behind someone who is deadlocking might have success sending a signal to the blocking process, unless they have committed to a non-reentrant exit routine

Re: Safety benefits of roundabouts

#80

Post by jgeada » Wed, Oct 25, 2023, 9:36 PM UTC

gnicholas wrote: post #17

Interesting that there are no listed downsides. I saw a more balanced article a while back and recall that it listed cost (especially of the additional real estate, since roundabouts are larger) as being one downside. And in built-up cities, it's basically impossible to convert traditional intersections to roundabouts, because there's simply no room. It is nice to not have to pay for replacement signals, or have to d…

There are roundabouts in England that are just a painted white circle in the middle of the intersection. Those work once the population knows how to handle roundabouts though. In the US, people barely comprehend regular roundabouts and in my town the larger one actually has traffic lights controlling the roundabout. So all the cost of the roundabout + all the cost of lights but none of the traffic flow benefits.