4 ms·

This is oddly timely. I'm travelling in Europe at the moment and have been covering a lot of area with a lot of roundabouts where they would be signaled or sign

by bane 2y ago

This is oddly timely. I'm travelling in Europe at the moment and have been covering a lot of area with a lot of roundabouts where they would be signaled or signed intersections in the US. They definitely make traffic flow smoothly and I've noticed a few areas where they are used to eliminate dangerous left turns at places like parking lots, you leave turning right, hit the next roundabout to "uturn" then head back the way you wanted to go. As a traffic device they really have lots of different kinds of use cases beyond just an alternative for a 4way. Where I grew up in a rural part of the US, we had one terrible 4-way intersection between two undevided highways. Over time they added lights, then experimented with different signaling systems, but every day it would back up for several miles in a couple directions, and add up to 30 minutes to some commutes. Then there were the inevitable accidents as people tried to rush it, making things worse all around. They replaced it with a roundabout about a decade ago, the population in the area also has increased dramatically in those years as farms turned into suburbs, but the backup is entirely gone. Theres no need any longer to maintain lights and switching systems, and the accidents are almost nil. Nobody has died there in years. People complained at first because it was "weird" then they realized they were complaining at home a half hour ealier than they would have been, so they stopped. They've since added a few more in the area and have even gotten very experimental with a double diamond interchange that's also done a lot of good. There's something in the water at the planners office. Seeing that transformation though and the immediate benefits has turned me into a lifetime fan of the roundabout.

rob74 2y ago
I'm living in Germany, where roundabouts are very popular with planners recently. I would say they definitely have their place, but they are also overused. The (smallish) city where I live has a bypass road where for some reason it was decided to use roundabouts (I suspect the same reason why it has so many tight curves - not wanting to purchase too much land). With the result that using the bypass is not much faster than driving through the town, so barely anyone uses it.
- consp 2y ago
  Sometimes roundabouts are used to limit traffic speed, since you MUST slow down, while keeping the same flow (for the calculated traffic throughput). Maybe that was the purpose. Roundabouts are generally more expensive than intersections due to needing more land works and more land than a normal cross intersection.
  - rob74 2y ago
    I don't know if that was the purpose or just a side effect, but I would have thought that the purpose of a bypass is to provide a more attractive route than the one going through the town center (so motorists have an incentive to use it), and having to slow down at the roundabouts (along with the mentioned tight curves and the 60 km/h speed limit) completely destroys the attractivity.
    - skeeter2020 2y ago
      drivers may interpret it differently, but flow is typically faster than stop&go, plus the illusion of "if you're moving you're getting somewhere" helps.
  - steelframe 2y ago
    > since you MUST slow down Where I live some of the locals treat a newly-built roundabout like the Daytona Speedway. It's almost as if their mentality is that you must NOT slow down, and they won't hesitate to express their displeasure at you if you happen to be "in their way" going the 15mph speed limit through the roundabout.
necrobrit 2y ago
The preference for 4 way stops in a country that otherwise prioritises traffic flow so much is really jarring. Traffic lights too to some extent. About 5 years ago my wife an I were doing a California road trip. At one point on a relatively rural road -- I think it might have been Dry Creek road heading into Napa but cannae mind exactly -- we got stuck in traffic for around 45 minutes. We thought there must have been some huge accident or roadworks closing the road. But got the the end and nope... 4 way stop essentially letting one. car. through. at. a. time. I distinctly remember exclaiming "why the f wasn't that a roundabout" after clearing. Funny that it is now one of my strongest memories of that trip haha.
- asib 2y ago
  4-way stops are bizarre to me having grown up in the UK where roundabouts/intersections with priority given for one direction are trusted and reliable traffic-calming measures. I think one of the reasons a 4-way stop might be introduced is to improve safety where there was previously a 2-way stop (that people would blow through). I came across this in Canada recently. All I can say is the UK has drastically lower traffic-related deaths than Canada [0] and I think I've seen 2-3 stop signs in my entire life. I imagine North America's pedestrian hostility is a piece of this puzzle. Don't get me started on North American highway interchanges. The UK's roundabout junction system is far superior, in my opinion. [0]: https://en.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...
  - lupusreal 2y ago
    Four way stops are common in lightly trafficked situations where the locals can't justify spending the money on anything but a few stop signs. For instance, the main street through a small town (<2k pop) might have traffic lights and maybe a circle for the one other major road it intersects, but where the two or three roads parallel to that intersect with other town roads, a four way stop makes the most sense. Most of the time a car gets to one, it will be alone. Since neither road is long and neither is expected to have fast cars anyway, a four way stop is the most natural and intuitive option way to sign it. Four way stops are also common when two country roads of relatively equal weight intersect. There are so many roads like that, so many intersections, that the local government can't possibly afford lights or circles on all of them. If one of the roads is known to get substantially more traffic than the other than a two-way stop is usually used, but if it isn't obvious then a four way stop is the safe default. In these situations, pedestrians aren't a factor at all because the intersection is five miles away from a town and it's farmland on both sides of both roads. Virtually nobody is walking there, not even people walking their dogs (unpaved access roads are better for that anyway.)
watwut 2y ago
> They definitely make traffic flow smoothly They make slow or medium traffic flow smoothly. If the traffic is heavy, roundabouts make everything worst.
- USiBqidmOOkAqRb 2y ago
  Have you measured it?
  - watwut 2y ago
    No, I got that from a materials road engineers made available publicly a while ago when I was interested in the topic. It had whole bunch of various trade-offs you can make with intersections in it.
    - USiBqidmOOkAqRb 2y ago
      Can we see it?
- jnovacho 2y ago
  Yep, in my city we have a roundabout with 4 cardinal directions, roughly aligned with compass directions. The West connection is to/from highway, so it has most traffic. People arriving from North/East/South want to leave on the West. And this causes massive jams, as the constant supply of traffic going from South entry to the West exit (i.e. doing left turn, and passing all ramps) essentially blocks all the other traffic. Roundabout are great, they increase safety of dangerous intersections. But sometimes a controlled intersection is just a better idea.
- 123pie123 2y ago
  the UK has traffic lights on certain heavily used roundabouts - sometime the lights will be temporary and only turn on once the throughput hits a certian level
- bane 2y ago
  I believe that I've read that elsewhere. They allow for better and higher flow than an intersection, but have a weird failure mode at very high rates where the circle gets loaded and all directions thus stop.
6LLvveMx2koXfwn 2y ago
We love a good roundabout in the UK, however it can be taken to extremes. The Magic Roundabout[1] in Hemel Hempstead is basically a roundabout made up of 6 mini-roundabouts. When it was first built locals used to sit in the middle watching the crashes. 1. https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempstead) https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempst...
- JdeBP 2y ago
  You're the 6th person so far to mention Hemel Hempstead; but it's a poor choice for a comment, because it's an extreme case. The normal and far more common occurrences of roundabouts in the U.K. support bane's point. Indeed, the junction in the headlined article is a slight variation on a quite common U.K. junction type: the double mini-roundabout. We can point to loads of them, such as this one in Bridgeyate (https://www.openstreetmap.org/#map=19/51.457696/-2.462268 https://www.openstreetmap.org/#map=19/51.457696/-2.462268) for just one random example. All of the WSDOT's points, about how large vehicles traverse them and how they are shaped like that because the staggered junction or slightly askew cross-roads that they replaced has space restrictions, apply to double mini-roundabouts. And as bane said, the research in the U.K. back in the 1970s when double mini-roundabouts were a new thing showed a significant reduction in accidents over the prior staggered junctions and askew crossroads, at less cost than enlarging the junctions. So the response is not to perplex the United Statians with Hemel Hempstead, but to welcome them to the shiny new future of 1970s road systems. And perhaps warn them that by the 1990s the road markings will have become a bit worn and scuffed by all of the HGVs driving over the centre. (-:
JohnClark1337 2y ago
[dead]

by bane 2y ago

rob74 2y ago

I'm living in Germany, where roundabouts are very popular with planners recently. I would say they definitely have their place, but they are also overused. The (smallish) city where I live has a bypass road where for some reason it was decided to use roundabouts (I suspect the same reason why it has so many tight curves - not wanting to purchase too much land). With the result that using the bypass is not much faster than driving through the town, so barely anyone uses it.

consp 2y ago
Sometimes roundabouts are used to limit traffic speed, since you MUST slow down, while keeping the same flow (for the calculated traffic throughput). Maybe that was the purpose. Roundabouts are generally more expensive than intersections due to needing more land works and more land than a normal cross intersection.
- rob74 2y ago
  I don't know if that was the purpose or just a side effect, but I would have thought that the purpose of a bypass is to provide a more attractive route than the one going through the town center (so motorists have an incentive to use it), and having to slow down at the roundabouts (along with the mentioned tight curves and the 60 km/h speed limit) completely destroys the attractivity.
  - skeeter2020 2y ago
    drivers may interpret it differently, but flow is typically faster than stop&go, plus the illusion of "if you're moving you're getting somewhere" helps.
- steelframe 2y ago
  > since you MUST slow down Where I live some of the locals treat a newly-built roundabout like the Daytona Speedway. It's almost as if their mentality is that you must NOT slow down, and they won't hesitate to express their displeasure at you if you happen to be "in their way" going the 15mph speed limit through the roundabout.

necrobrit 2y ago

The preference for 4 way stops in a country that otherwise prioritises traffic flow so much is really jarring. Traffic lights too to some extent. About 5 years ago my wife an I were doing a California road trip. At one point on a relatively rural road -- I think it might have been Dry Creek road heading into Napa but cannae mind exactly -- we got stuck in traffic for around 45 minutes. We thought there must have been some huge accident or roadworks closing the road. But got the the end and nope... 4 way stop essentially letting one. car. through. at. a. time. I distinctly remember exclaiming "why the f wasn't that a roundabout" after clearing. Funny that it is now one of my strongest memories of that trip haha.

asib 2y ago
4-way stops are bizarre to me having grown up in the UK where roundabouts/intersections with priority given for one direction are trusted and reliable traffic-calming measures. I think one of the reasons a 4-way stop might be introduced is to improve safety where there was previously a 2-way stop (that people would blow through). I came across this in Canada recently. All I can say is the UK has drastically lower traffic-related deaths than Canada [0] and I think I've seen 2-3 stop signs in my entire life. I imagine North America's pedestrian hostility is a piece of this puzzle. Don't get me started on North American highway interchanges. The UK's roundabout junction system is far superior, in my opinion. [0]: https://en.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...
- lupusreal 2y ago
  Four way stops are common in lightly trafficked situations where the locals can't justify spending the money on anything but a few stop signs. For instance, the main street through a small town (<2k pop) might have traffic lights and maybe a circle for the one other major road it intersects, but where the two or three roads parallel to that intersect with other town roads, a four way stop makes the most sense. Most of the time a car gets to one, it will be alone. Since neither road is long and neither is expected to have fast cars anyway, a four way stop is the most natural and intuitive option way to sign it. Four way stops are also common when two country roads of relatively equal weight intersect. There are so many roads like that, so many intersections, that the local government can't possibly afford lights or circles on all of them. If one of the roads is known to get substantially more traffic than the other than a two-way stop is usually used, but if it isn't obvious then a four way stop is the safe default. In these situations, pedestrians aren't a factor at all because the intersection is five miles away from a town and it's farmland on both sides of both roads. Virtually nobody is walking there, not even people walking their dogs (unpaved access roads are better for that anyway.)

watwut 2y ago

> They definitely make traffic flow smoothly They make slow or medium traffic flow smoothly. If the traffic is heavy, roundabouts make everything worst.

USiBqidmOOkAqRb 2y ago
Have you measured it?
- watwut 2y ago
  No, I got that from a materials road engineers made available publicly a while ago when I was interested in the topic. It had whole bunch of various trade-offs you can make with intersections in it.
  - USiBqidmOOkAqRb 2y ago
    Can we see it?
jnovacho 2y ago
Yep, in my city we have a roundabout with 4 cardinal directions, roughly aligned with compass directions. The West connection is to/from highway, so it has most traffic. People arriving from North/East/South want to leave on the West. And this causes massive jams, as the constant supply of traffic going from South entry to the West exit (i.e. doing left turn, and passing all ramps) essentially blocks all the other traffic. Roundabout are great, they increase safety of dangerous intersections. But sometimes a controlled intersection is just a better idea.
123pie123 2y ago
the UK has traffic lights on certain heavily used roundabouts - sometime the lights will be temporary and only turn on once the throughput hits a certian level
bane 2y ago
I believe that I've read that elsewhere. They allow for better and higher flow than an intersection, but have a weird failure mode at very high rates where the circle gets loaded and all directions thus stop.

6LLvveMx2koXfwn 2y ago

We love a good roundabout in the UK, however it can be taken to extremes. The Magic Roundabout[1] in Hemel Hempstead is basically a roundabout made up of 6 mini-roundabouts. When it was first built locals used to sit in the middle watching the crashes. 1. https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempstead) https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempst...

JdeBP 2y ago
You're the 6th person so far to mention Hemel Hempstead; but it's a poor choice for a comment, because it's an extreme case. The normal and far more common occurrences of roundabouts in the U.K. support bane's point. Indeed, the junction in the headlined article is a slight variation on a quite common U.K. junction type: the double mini-roundabout. We can point to loads of them, such as this one in Bridgeyate (https://www.openstreetmap.org/#map=19/51.457696/-2.462268 https://www.openstreetmap.org/#map=19/51.457696/-2.462268) for just one random example. All of the WSDOT's points, about how large vehicles traverse them and how they are shaped like that because the staggered junction or slightly askew cross-roads that they replaced has space restrictions, apply to double mini-roundabouts. And as bane said, the research in the U.K. back in the 1970s when double mini-roundabouts were a new thing showed a significant reduction in accidents over the prior staggered junctions and askew crossroads, at less cost than enlarging the junctions. So the response is not to perplex the United Statians with Hemel Hempstead, but to welcome them to the shiny new future of 1970s road systems. And perhaps warn them that by the 1990s the road markings will have become a bit worn and scuffed by all of the HGVs driving over the centre. (-:

JohnClark1337 2y ago

[dead]