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Safety benefits of roundabouts

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Re: Safety benefits of roundabouts

#91

Post by kieranmaine »

swatcoder wrote: post #45
polemic wrote: post #31

Earlier quoted context omitted.

Roundabouts are great (and common where I live), but a downside is they can be difficult for pedestrians to cross. You need crossings that are set back from the exits, but this also makes it a longer path for the pedestrian.

Yes, they're absolutely horrid for pedestrians. Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross, and any pedestrian crossing the outflow of a roundabout can trigger a traffic backup that interferes with the flow of the circle itself and surprise drivers who expect it to stay moving. They have their benefits in some intersections, but they also have tr…

I disagree. As a pedestrian, I only have to worry about cars coming from 2 directions (on to/off the roundabout) instead of 4 at an intersection.

I'm confused by your comment that drivers merging into a roundabout are too distracted.

As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off the roundabout I only have to check for pedestrians crossing the exit I want to take.

At an intersection, all these checks are mashed together into. I have to keep track of all the cars at the intersection plus the pedestrians that may be crossing in front of me and the exit I want to take.

Re: Safety benefits of roundabouts

#92

Post by josephg »

rwmj wrote: post #11

If you like roundabouts, try a roundabout of roundabouts: https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempst... This is near where I live and it is indeed safe, mainly because everyone drives incredibly slowly and cautiously since the experience is scary as hell.

> because everyone drives incredibly slowly and cautiously since the experience is scary as hell

Apparently there are fewer accidents on the roads when the traffic lights aren’t working. The reason is exactly that - everyone is terrified and drives really slowly to make up for it.

Re: Safety benefits of roundabouts

#93

Post by NBJack »

Arrath wrote: post #61
marginalia_nu wrote: post #60

Earlier quoted context omitted.

Well, when you mention it, I do think it's possible to join these 3d roundabouts into a 4d roundabout, essentially putting them on the vertices of a tesseract, permitting drivers in 4 dimensional space to safely meet on the 3d-dimensional surface of a 4-dimensional hyper-sphere. Of course it's a real spaghetti intersection where you need to potentially navigate dozens of 2D roundabouts to get to any given direction.…

"And that, kids, is the story of how I T-boned myself."

Bonus points if we make one of our dimensions time, and now have to exchange insurance information with a very grumpy future version of yourself.

Re: Safety benefits of roundabouts

#94

Post by ghaff »

macleginn wrote: post #25
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.

With lively enough traffic, it’s not rare to see several cars waiting for their turn to enter the roundabout.

On my way into the city, there is a rotary that at rush hour can be a 15+ minute wait to enter the rotary in the direction of the heavy traffic flow.

Re: Safety benefits of roundabouts

#95

Post by josephg »

DavidVoid wrote: post #55
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…

> they include rather obscure rules as to which lane you are allowed to drive in at any moment and americans do not like to learn new rules. Do they? I guess it probably depends on the country. Here in Sweden I'm pretty sure you can drive in whatever lane you like (unless they're explicitly labeled). But normal lane-swithching rules apply ofc and, importantly, when you enter a roundabout you have to yield to traffic…

Yeah here in Australia, 2 lane roundabouts usually require that people taking the 1st exit use the outermost lane and people using the 3rd+ exits use the inner lane of the roundabout. (And if you’re going straight you can use either). If you’re in the inner lane of the roundabout and want to leave, you usually don’t change lane while in the roundabout, but signal and exit by cutting across the outer lane on your way out.

Re: Safety benefits of roundabouts

#96

Post by ghaff »

kieranmaine wrote: post #91
swatcoder wrote: post #45

Earlier quoted context omitted.

Yes, they're absolutely horrid for pedestrians. Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross, and any pedestrian crossing the outflow of a roundabout can trigger a traffic backup that interferes with the flow of the circle itself and surprise drivers who expect it to stay moving. They have their benefits in some intersections, but they also have tr…

I disagree. As a pedestrian, I only have to worry about cars coming from 2 directions (on to/off the roundabout) instead of 4 at an intersection. I'm confused by your comment that drivers merging into a roundabout are too distracted. As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off th…

It depends on the roundabout. A low traffic, single-lane roundabout is pretty straightforward. There are also heavy traffic two-lane roundabouts in my area. One is pretty much impossible for a pedestrian to traverse. (Not that it's in a pedestrianized area anyway.) The other two can only be traversed at relatively nearby traffic lights.

Re: Safety benefits of roundabouts

#97

Post by Gare »

tunesmith wrote: post #81

Two-lane roundabouts still confuse me a bit. Even the video tutorial in that article has what looks like a problem to me. At 1:06, the pink car in the right lane skips the first exit. How does the orange car in the left lane know it's safe to take the second exit? That's a collision risk right there if the pink car wants to continue counter-clockwise.

It is now considered that multi-lane roundabouts (which permit lane changing in the roundabout) are a bad idea because they have too many collision points. Turbo-roundabout is a much better alternative: https://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts

Re: Safety benefits of roundabouts

#98

Post by throw0101a »

devnull3 wrote: post #78
throw0101a wrote: post #74

Earlier quoted context omitted.

"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,…

I meant how the straight-through part deals with yielding and such, but I see that it is (like) a signalled/lighted intersection.

Re: Safety benefits of roundabouts

#99

Post by swatcoder »

kieranmaine wrote: post #91
swatcoder wrote: post #45

Earlier quoted context omitted.

Yes, they're absolutely horrid for pedestrians. Drivers anticipating their merge into roundabout are often too distracted to notice pedestrians intending to cross, and any pedestrian crossing the outflow of a roundabout can trigger a traffic backup that interferes with the flow of the circle itself and surprise drivers who expect it to stay moving. They have their benefits in some intersections, but they also have tr…

I disagree. As a pedestrian, I only have to worry about cars coming from 2 directions (on to/off the roundabout) instead of 4 at an intersection. I'm confused by your comment that drivers merging into a roundabout are too distracted. As a driver merging into a roundabout I find I have far less cognitive load. I only have to look for pedestrians crossing in front of me and cars coming from the left. When coming off th…

With the exception of decorative 1-lane roundabouts in sleepy residential neighborhoods, all the roundabouts I encounter in Central and Southern California are 2-3 lane circles with various lane->exit mappings, some of which overlap and some of which are exclusive.

Drivers coming into them, who want to actually benefit from the roundabout and not just turn it into an awkward stop sign, are responsible for reversing the exit to lane mapping, then timing their approach to the intersection with an opening that will let them reach to their lane while maintaining a flow. If they can't manage to do that, of course they're supposed to stop and yield until an appropriate opening becomes available.

Inevitably, the designated pedestrian crosswalk is some 5-10+ feet prior to where the car would have to stop if it does need to yield while awaiting an opening.

Compared to a signaled intersection or a 2/4-way stop, where the pedestrian crossing coincides with a natural traffic stop, this basically means that approximately zero cars actually stop for pedestrians. Some are too busy to notice and others just don't want to have to deal with a stop and so ignore their responsibility.

I assume you must live somewhere else, where roundabouts are smaller and play some different role than here.

Re: Safety benefits of roundabouts

#100

Post by ajb »

cryptoegorophy wrote: post #46
rwmj wrote: post #11

If you like roundabouts, try a roundabout of roundabouts: https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempst... This is near where I live and it is indeed safe, mainly because everyone drives incredibly slowly and cautiously since the experience is scary as hell.

How is it even legal? You need a special school just for this one 99lvl king of the roundabouts

You only need to know one fact to navigate it: the middle is not a roundabout, ignore the fact that it is round.

Every driver in the UK is used to sequences of two or three roundabouts, they are part of the driving test. As long as you are not bamboozled by the pseudo roundabout in the middle, you just navigate it based on principles you already know.

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