4 ms·

If you like roundabouts, try a roundabout of roundabouts: https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempstead) https://en.wikipedia.org/wiki/Magic_R

by rwmj 3y ago

If you like roundabouts, try a roundabout of roundabouts: https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempstead) 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.

marginalia_nu 3y ago
Using roundabouts of roundabouts it's actually possible to build a 3 dimensional roundabout where traffic along the x, y and z axis can safely meet on the surface of a sphere.
- Arrath 3y ago
  Please, the average driver has trouble enough merging into traffic.
  - marginalia_nu 3y ago
    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. Which coincidentally also is true for the 2D road network where I live.
    - Arrath 3y ago
      "And that, kids, is the story of how I T-boned myself."
      - marginalia_nu 3y ago
        Now you're thinking with portals!
      - NBJack 3y ago
        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.
- adrianmonk 3y ago
  Can you build a 4 dimensional one on a hypersphere, so that traffic can go around in circles in time? Bonus question: if you can, what happens if you drive a DeLorean at 88 miles/hour on it?
cryptoegorophy 3y ago
How is it even legal? You need a special school just for this one 99lvl king of the roundabouts
- ajb 3y ago
  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.
  - Moru 3y ago
    As a right hand driver since 40 years I can't wrap my head around the combo roundabouts. I get terrified just looking at youtube drivers trying to explain how they work in England.
    - daveoc64 3y ago
      From experience, there's a lot of people in the UK that don't truly know what to do at a double mini roundabout. As other comments have noted, when drivers are less clear on the rules they tend to drive more slowly and cautiously - I think that makes double roundabouts "work out" most of the time.
    - ajb 3y ago
      You do need to practice them. When I was learning my instructor devoted significant time to them. If you come from a country that doesn't have them, it's not irrational to worry that you aren't going to pick up how to manage them instantly. You need to make several decisions in succession, at the same time as doing several lane merges. But they're not rocket science. If you make a simple mistake, you just end up going the wrong way and have to turn round somewhere. Holders of foreign driving licences should probably be required to do a course, including these at least, before being allowed to use their licence here.
josephg 3y ago
> 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.
- da768 3y ago
  Over here everyone takes dead lights for green lights/no lights
- Clamchop 3y ago
  I've read that yields can often be safer than stop signs for the same reason.
  - Moru 3y ago
    Just to throw off the statistics: We have a road in town that used to be a straight run through the forest. Suddently it got a yield sign and a bus road crossing it. This ofcourse lead to a number of accidents with cars driving into busses not noticing the yield sign. So next step was stop signs. Still lots of accidents though, since this road has been alone so long and was built for 70 km/h from the start so you don't get any hints about that you should slow down. Then came the thick white lines across the road at regular intervals before the crossing. Still accidents. Now they built some stone divider between the lanes so you have to go a little to the side and can't blow straight through the crossing. I'm just waiting for the speed bumps, that is usually the first stage already, bit confusing that they didn't do that yet.
hermitcrab 3y ago
Swindon laughs at Hemel's sad excuse for a magic roundabout. The true roundabout connoisseur knows that the roundabouts should overlap.
VincentEvans 3y ago
I’ve always thought that the safety effect of the roundabouts - is not anything related to it’s traffic flow properties, but rather the fact that roundabouts are confusing and people slow down and proceed with caution. We could accomplish the same with other forms of creative driver-hostile road construction and deliberately unproductive signage.

by rwmj 3y ago

marginalia_nu 3y ago

Using roundabouts of roundabouts it's actually possible to build a 3 dimensional roundabout where traffic along the x, y and z axis can safely meet on the surface of a sphere.

Arrath 3y ago
Please, the average driver has trouble enough merging into traffic.
- marginalia_nu 3y ago
  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. Which coincidentally also is true for the 2D road network where I live.
  - Arrath 3y ago
    "And that, kids, is the story of how I T-boned myself."
    - marginalia_nu 3y ago
      Now you're thinking with portals!
    - NBJack 3y ago
      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.
adrianmonk 3y ago
Can you build a 4 dimensional one on a hypersphere, so that traffic can go around in circles in time? Bonus question: if you can, what happens if you drive a DeLorean at 88 miles/hour on it?

cryptoegorophy 3y ago

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

ajb 3y ago
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.
- Moru 3y ago
  As a right hand driver since 40 years I can't wrap my head around the combo roundabouts. I get terrified just looking at youtube drivers trying to explain how they work in England.
  - daveoc64 3y ago
    From experience, there's a lot of people in the UK that don't truly know what to do at a double mini roundabout. As other comments have noted, when drivers are less clear on the rules they tend to drive more slowly and cautiously - I think that makes double roundabouts "work out" most of the time.
  - ajb 3y ago
    You do need to practice them. When I was learning my instructor devoted significant time to them. If you come from a country that doesn't have them, it's not irrational to worry that you aren't going to pick up how to manage them instantly. You need to make several decisions in succession, at the same time as doing several lane merges. But they're not rocket science. If you make a simple mistake, you just end up going the wrong way and have to turn round somewhere. Holders of foreign driving licences should probably be required to do a course, including these at least, before being allowed to use their licence here.

josephg 3y ago

> 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.

da768 3y ago
Over here everyone takes dead lights for green lights/no lights
Clamchop 3y ago
I've read that yields can often be safer than stop signs for the same reason.
- Moru 3y ago
  Just to throw off the statistics: We have a road in town that used to be a straight run through the forest. Suddently it got a yield sign and a bus road crossing it. This ofcourse lead to a number of accidents with cars driving into busses not noticing the yield sign. So next step was stop signs. Still lots of accidents though, since this road has been alone so long and was built for 70 km/h from the start so you don't get any hints about that you should slow down. Then came the thick white lines across the road at regular intervals before the crossing. Still accidents. Now they built some stone divider between the lanes so you have to go a little to the side and can't blow straight through the crossing. I'm just waiting for the speed bumps, that is usually the first stage already, bit confusing that they didn't do that yet.

hermitcrab 3y ago

Swindon laughs at Hemel's sad excuse for a magic roundabout. The true roundabout connoisseur knows that the roundabouts should overlap.

VincentEvans 3y ago

I’ve always thought that the safety effect of the roundabouts - is not anything related to it’s traffic flow properties, but rather the fact that roundabouts are confusing and people slow down and proceed with caution. We could accomplish the same with other forms of creative driver-hostile road construction and deliberately unproductive signage.