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Magic Roundabout (Swindon)

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Re: Magic Roundabout (Swindon)

#181

Post by throw0101a »

martijn9612 wrote: post #160
matthewowen wrote: post #92

Earlier quoted context omitted.

This style exists in the UK too: near where I group is https://maps.app.goo.gl/hjhi3gQijUGnuXha7 and a bunch of others like it: five roads in and out, with lanes that naturally flare out (though with the option to cut over right to continue further round). Quite intimidating when you're learning to drive. That said, my recollection is that the default in the UK is that lanes flare out from the center, so that once yo…

Having lights there defeats a lot of the roundabout. The turboroundabout definitely does not have traffic lights. Look at this[0] implementation, the one you linked qualifies as a "turboplein". [0] https://www.google.com/maps/place/Energieweg,+Nijmegen/@51.8...

> Having lights there defeats a lot of the roundabout.

You're not wrong, but roundabouts degraded the busier they get:

> As at other forms of unsignalized intersection, when traffic flows on an approach exceed approximately 85 percent of capacity, delays and queue lengths vary significantly about their mean values (with standard deviations of similar magnitude as the means). For this reason, the analysis procedures in some countries (Australia, Germany, and the United Kingdom), and this guide, recommend that roundabouts be designed to operate at no more than 85 percent of their estimated capacity.

* https://www.fhwa.dot.gov/publications/research/safety/00067/...

1-, 2-, and 3-lane RAs each have different capacities, and it may not be easy to expand one size to the next larger one depending on what else is in the area, so signals can allow for the general architecture of RAs to be extended without major changes besides putting up some poles and wires.

Re: Magic Roundabout (Swindon)

#182

Post by snowwrestler »

ken wrote: post #78
snowwrestler wrote: post #61

> however, the roundabout provides a better throughput of traffic than other designs and has an excellent safety record, since traffic moves too slowly to do serious damage in the event of a collision. In 2010, the National Cooperative Highway Research Program concluded that the roundabout reduces injurious crashes by three quarters. One of the hardest things in local democracy is that the best traffic patterns are o…

The problem, as always, is that parties disagree on what "best" means. Governments and safety organizations are pushing for "Vision Zero", i.e., safety at any cost. (My economics professor once pointed out that if you really want zero traffic deaths, just limit all cars to 5 mph everywhere.) For people driving on the road, the current level of risk (roughly 1 death per 100M miles) is acceptable, and arriving quickly…

I think characterizing "Vision Zero" as "safety at any cost" neatly illustrates what I'm saying about the local politics of traffic.

(It is an explicit component of Vision Zero that improved safety should not be expensive to communities.)

Re: Magic Roundabout (Swindon)

#183

Post by throw0101a »

TheCapn wrote: post #83
kerkeslager wrote: post #53

I guess what this shows is two things: 1. Scaring people into slowing down is a viable way to avoid accidents. 2. Perceived scariness of an intersection is not indicative of how dangerous it actually is.

RE: #2 Absolutely. Within Saskatchewan, east of Regina, we just completed three new bridges for suburban communities to access the main highway. In two of the three bridges were atypical designs using a Diverging Diamond at one point, and dual roundabouts at the other. When announced lots of people were fearful of the new designs and there was unsurprisingly a lot of outcry from ninnies who were afraid of the unknown…

> Within Saskatchewan, east of Regina ...

Is it possible to get (Google?) Maps links for these?

Re: Magic Roundabout (Swindon)

#184

Post by Sohcahtoa82 »

jiveturkey wrote: post #138
mcv wrote: post #43

A better solution for high traffic flow is the turbo roundabout[0] which is getting increasingly popular in Netherland. Before you enter the roundabout, you select the lane for the direction you want to go. You only cross traffic when entering the roundabout for the first time. After that, you simply follow your lane and it delivery you where you want to go. It looks complicated from above, but it's very simple once…

I don't like it. From the bottom, if you want to go straight you enter on the right lane. From the right, if you want to go straight you enter on the left lane. This lack of symmetry means you need to be very familiar with the path in advance, and not get confused about which orientation you're in. For the signage to be far enough from the roundabout to get your bearings in time, it will be too far for most people to…

> late merge asshole problem.

Early mergers are the assholes. You're SUPPOSED to merge late. If you see a sign saying "Construction ahead 3 miles, left lane closed" or something, and you immediately start trying to merge, you're the one doing it wrong.

Early merging creates unpredictability in traffic flow. Zipper merges are safer and lead to shorter merge queues. https://en.wikipedia.org/wiki/Merge_(traffic)#Zipper

Re: Magic Roundabout (Swindon)

#185

Post by frosted-flakes »

Sohcahtoa82 wrote: post #184
jiveturkey wrote: post #138

Earlier quoted context omitted.

I don't like it. From the bottom, if you want to go straight you enter on the right lane. From the right, if you want to go straight you enter on the left lane. This lack of symmetry means you need to be very familiar with the path in advance, and not get confused about which orientation you're in. For the signage to be far enough from the roundabout to get your bearings in time, it will be too far for most people to…

> late merge asshole problem. Early mergers are the assholes. You're SUPPOSED to merge late. If you see a sign saying "Construction ahead 3 miles, left lane closed" or something, and you immediately start trying to merge, you're the one doing it wrong . Early merging creates unpredictability in traffic flow. Zipper merges are safer and lead to shorter merge queues. https://en.wikipedia.org/wiki/Merge_(traffic)#Zipper

There's a difference between late merges and late lane changes, which is what OP meant. When all vehicles are merging into one lane, sure, the zipper merge is superior. But when you realise you're in the wrong lane right before an intersection and try to force your way over, that's the problem.

Re: Magic Roundabout (Swindon)

#186

Post by Sohcahtoa82 »

frosted-flakes wrote: post #185
Sohcahtoa82 wrote: post #184

Earlier quoted context omitted.

> late merge asshole problem. Early mergers are the assholes. You're SUPPOSED to merge late. If you see a sign saying "Construction ahead 3 miles, left lane closed" or something, and you immediately start trying to merge, you're the one doing it wrong . Early merging creates unpredictability in traffic flow. Zipper merges are safer and lead to shorter merge queues. https://en.wikipedia.org/wiki/Merge_(traffic)#Zipper

There's a difference between late merges and late lane changes , which is what OP meant. When all vehicles are merging into one lane, sure, the zipper merge is superior. But when you realise you're in the wrong lane right before an intersection and try to force your way over, that's the problem.

> There's a difference between late merges and late lane changes

Starting to go off topic, but I'm starting to feel I'm the only person the never refers to a lane change as a merge when it isn't a part of a lane ending. IMO, a "merge" should only refer to lanes ending. Otherwise, fighting about "late merging" becomes ambiguous.

Re: Magic Roundabout (Swindon)

#188

Post by laumars »

twic wrote: post #132
laumars wrote: post #5

Earlier quoted context omitted.

The beauty of these kind of junctions is you can drive clockwise or anti-clockwise. Essentially it's not a roundabout but rather one junction comprised of lots of roundabouts. The Colchester equivalent better demonstrates this: https://en.wikipedia.org/wiki/Magic_Roundabout_(Colchester) Personal anecdote: I had to drive around one of these junctions during my driving test

In other Colchester roundabout news, the one at North Station is fun - it's a normal roundabout, but with a road cutting right through the middle of it too: https://www.youhaventlived.com/qblog/2005/QBlog160705A.html There are lights to make sure nobody crashes - effectively switching it between being a roundabout and being a through road - but it's still pretty weird.

I worked in Colchester around the time that was being built. It's much nicer now than what was there before (in my opinion). The only annoying thing about that junction is it can sometimes take a long time to traverse it because of all the lights.

The problem with Colchester is that it's plagued with heavy traffic and bad drivers.

Re: Magic Roundabout (Swindon)

#189

Post by Doxin »

tzs wrote: post #140
mcv wrote: post #43

A better solution for high traffic flow is the turbo roundabout[0] which is getting increasingly popular in Netherland. Before you enter the roundabout, you select the lane for the direction you want to go. You only cross traffic when entering the roundabout for the first time. After that, you simply follow your lane and it delivery you where you want to go. It looks complicated from above, but it's very simple once…

> There's no possibility to keep going around until you figure out where you want to go. I assume that traffic on the loops always has the right of way over traffic trying to enter the loops? In that case, why can't you keep going around? At the place where the northbound inner loop becomes the southbound outer loop, it crosses the start of the southbound inner loop. The cars coming from the south trying to enter the…

You're not allowed to change lane once you've entered this type of roundabout. In practice the lanes are separated by a curb. Of course you still can change lane at the points where traffic joins the roundabout, but it's a sharp 90 degree turn and you'll discover real soon that it's a mistake to try.

Re: Magic Roundabout (Swindon)

#190

Post by andybak »

chrisseaton wrote: post #39
andybak wrote: post #36

Earlier quoted context omitted.

What about the fact it has two lanes?

How's is it different to any other road with two lanes? If you're about to turn off then be on the inside lane. If you're not turning off then be on the outside lane.

On a roundabout there's usually not enough time to consider turning off as two separate maneuvers. Instead you follow certain rules and it "just works".

i.e. join on the outside lane if you're turning off immediately and join the inside lane otherwise.

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