

Magic Roundabout - subsystem
http://en.wikipedia.org/wiki/Magic_Roundabout_(Swindon)

======
polyfractal
As a child, I lived in England for a brief stint (around a year) because my
dad was transferred to his company's British branch. We lived somewhere near
the Magic Roundabout (Bovingdon, which I think is pretty close).

We had just moved, so both of my parents were still getting used to driving on
the opposite side of the road. And roundabouts in general. I have fond
memories of my mom getting stuck on the Magic Roundabout for about an hour,
too terrified to leave. So we just kept going round and round and round. Being
a small child (3 or 4 years old), I just kept telling her every-time we passed
the same building.

 _"Mommy! There's that building again!"._

I'm sure she wanted to reach back and strangle me. When she eventually
mustered the courage to exit...she did something wrong and we stopped up the
whole roundabout. I don't actually remember that part, but she claims traffic
basically ground to a halt until she maneuvered her car out of traffic.

Fond memories =)

Edit: Based on another commenter, looks like it was the "Plough" roundabout,
not the one in this article. Whoops!

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Jabbles
This is basically two normal roundabouts, one inside the other, with traffic
direction the opposite way in the inner lane. Or a two-lane roundabout. It
allows you to spend less time on the roundabout if you want to take the
junction to your right, as you would usually have to go to your left and do an
almost complete lap.

Compare reaching your parent on a singly-linked list to a doubly-linked list.
Being able to traverse in either direction may provide significant performance
boosts...

~~~
ZeroGravitas
Going by the diagram, I think it makes more sense to think of it as 6
roundabouts in a circle. The inner "reverse roundabout" is just you entering
and leaving each roundabout by the first exit in turn. The "outer roundabout"
is similarly you entering and leaving via the second exit of each roundabout.
Neither of those is a true roundabout as you don't have right of way once
you're on it.

~~~
dllthomas
In terms of driving, the five-roundabout perspective makes more sense (for
reasons of right-of-way, as you say). In terms of algorithmic complexity, if
we are considering distance traveled by the average vehicle, the two-nested-
roundabouts perspective makes more sense.

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pcowans
I used to live close to this one:
<http://en.wikipedia.org/wiki/Magic_Roundabout_(Colchester)> \- it's actually
very easy to do, and is really nothing more than a road that happens to run in
a loop and has 5 small roundabouts on it. The junction in the current
configuration works a lot better than it did when it was a large regular
roundabout, as the pattern of traffic made it almost completely impossible to
enter the roundabout at some of the entrances.

~~~
andyhmltn
That's the one I'm near too. It isn't actually that hard. You just need to
treat it as a normal road and not a big roundabout.

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MrMember
After studying it for a bit it isn't too difficult to figure out how it works,
and I'm sure if you drove through it every day it would even become boring,
but if I encountered this roundabout blind without knowing anything about it
I'd probably cause some sort of accident.

~~~
dsr_
Most people slow down.

Slowing down means more time for observation and reaction. As a result, it's
actually quite a safe interchange.

(Most traffic accidents are the result of inattention coupled with
insufficient reaction time. If you aren't paying attention, bad things happen.
If you are paying attention but there isn't enough time to do anything about
it, bad things happen. Thus, safety is highly correlated with both getting
driver attention and increasing the time available for reacting.

Narrow twisty mountain roads are often much safer than the country roads
leading up to them -- because drivers know they need to be involved and aware.
Long straight highways are safe at high speeds because drivers can see
obstructions and changes far in advance.

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js2
Raleigh, NC installed a two-lane roundabout a couple years ago[1]. Drivers
could not handle it[2] (almost daily crashes) and it had to be reduced to a
single-lane roundabout[3]. I can't imagine what Raleigh drivers would do faced
with the Magic Roundabout.

1\.
[http://www2.acs.ncsu.edu/trans/planning/construction/Brochur...](http://www2.acs.ncsu.edu/trans/planning/construction/Brochure%20revised%206-16-10_1.pdf)

2\.
[http://www.raleighpublicrecord.org/news/2011/09/12/accident-...](http://www.raleighpublicrecord.org/news/2011/09/12/accident-
numbers-at-hillsborough-roundabout-higher-than-expected/)

3\. [http://www.newsobserver.com/2012/07/25/2218567/crash-
prone-r...](http://www.newsobserver.com/2012/07/25/2218567/crash-prone-
roundabout-in-raleigh.html)

~~~
jdpage
There's been a bit of a roundabout fad in the Triangle area, actually. They
installed a couple in Wake Forest (a nearby town), and there's actually three
near the spot you mentioned now. As a British expat, I am personally fine with
them, but people around here do tend to have issues with them.

The upshot of this is that one of the most terrifying things I've done
recently was to try to navigate all three of the roundabouts, in succession,
on a bicycle, at the same time as two or three buses.

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dfan
I wonder if the 5/4 meter of the XTC song "English Roundabout"
<http://www.youtube.com/watch?v=akrD84P_zxU> (they're from Swindon and the
Wikipedia page mentions that the song is a tribute) is a reference to the 5
external roundabouts.

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deltasquared
I have been there once. It was the scariest roundabout I have traversed. The
contra rotating flow (inside goes one way, outside goes the other) makes it
extra exciting.

~~~
meaty
Myself too. Hangar Lane is far scarier as the driving mentality is central
London style and there are 7 lanes.

~~~
alexkus
Hanger Lane is scary as most drivers haven't realised that it's not really a
(proper) roundabout any more.

On a normal roundabout if you stay in a lane (one of the inside ones at least)
you'll just keep going round and round.

With the redesigned Hanger Lane you get in the lane marked for your exit and
the outer lanes slowly peel off as feeders for the appropriate turnings. If
you want to keep going round and round you'll need to keep moving over to the
right (since we go round them clockwise) every so often to keep from being
directed off eventually from your current lane.

[EDIT] It's a "Spiral Roundabout".

~~~
smikhanov
Isn't every big roundabout the same? I drive via Old Street roundabout in
London almost every day and it certainly is spiraling. When I took my driving
lessons a year ago, my instructor was saying this configuration is pretty
normal.

~~~
thisone
not really, being from the US and now living in the UK, the "traffic circles"
I've gone round in the US were really just circular roads with one lane of
traffic and easy to get stuck on if it's busy and you stray too far to the
center. Quite different from UK roundabouts.

Not saying all US traffic circles are like that of course.

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alexjeffrey
being from Swindon, I'm very proud to see this on the frontpage of hacker
news! I took my driving test on it...

It's actually a lot easier to navigate than it looks, you can essentially
treat the whole thing as one giant roundabout by taking the second exit on
each mini-roundabout.

~~~
OliC
I too took my driving test on this beast. I spent a good part of a driving
lesson learning the different routes across it.

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mootothemax
I went round a similar system first thing on Tuesday morning, the Plough
roundabout in Hemel Hempstead:

[http://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempste...](http://en.wikipedia.org/wiki/Magic_Roundabout_\(Hemel_Hempstead\))

Driving through was surprisingly easy (not to mention efficient), especially
given how chaotic morning rush-hour driving can be.

~~~
mwilliamson
When I was learning to drive (in Hemel Hempstead), I found it easier to get
around the magic roundabout if you just thought about it as a road that
happened to be a small circle with a few mini-roundabouts on it. Even when
it's busy, I've found it quite straightforward to get around, mainly because
you rarely have to wait long at a mini-roundabout (if the car to your left is
turning right, you can start going since the car on the right is blocked).

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laacz
If you consider that I'm from the part of the world where everybody is driving
on the right side (see what I did there?:) of the road, it was not a complete
disaster. Up and close this magic roundabout actually is not so magic - just
one large roundabout with few smaller entry/exit roundabouts. Though, first
timers could easily drive round and round for a while.

~~~
mdda
The UK is not exactly alone in driving on the left : Nations like Japan, India
and Indonesia keep it company (among the 76 [0])...

One explanation that always made sense to me is that when driving a
manual/stick-shift car, taking your dominant hand (statistically the right
hand) off the steering wheel for a secondary task like changing gear is more
dangerous... YMMV

[0] [http://en.wikipedia.org/wiki/Right-_and_left-
hand_traffic#Ju...](http://en.wikipedia.org/wiki/Right-_and_left-
hand_traffic#Jurisdictions_with_left-hand_traffic)

~~~
laacz
Yes, I'm informed. This comment was not ment to be insulting to those who
drive on the wro.. left side of the road. Just an observation of specific
roundabout from a person, who drives on right one each day.

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goatforce5
Similarly interesting/confusing is the Traffic Light Tree that was in Canary
Wharf, London. It's recently been removed to make way for some roadworks.

<http://en.wikipedia.org/wiki/Traffic_Light_tree>

Note that it's art rather than something functional.

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lucvh
We have a similar roundabout in Colchester where your driving instructor would
take you if you were being cocky. It is actually incredibly easy to use if you
treat it as a load of mini roundabouts.

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ck2
worth 1000 words:
[http://www.youtube.com/results?search_query=Magic+Roundabout...](http://www.youtube.com/results?search_query=Magic+Roundabout+Swindon)

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skywalk
It's funny how this ended up on here - this article about "nail houses" was
recently posted today: <http://news.ycombinator.com/item?id=4915398>

The magic roundabout is mentioned in another posting on that same site:
[http://www.theworldgeography.com/2011/08/top-10-strange-
stre...](http://www.theworldgeography.com/2011/08/top-10-strange-streets-of-
world.html)

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andyhmltn
We must go deeper. But seriously, are they all that rare? There's one similar
just down the road from me (Colchester) and it's a pain when you're learning
to drive.

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gadders
Isn't there another one of these in Essex somewhere, other than Colchester? I
seem to remember passing it on the way to Canvey.

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wowfat
Watch this <http://www.youtube.com/watch?v=kPANKRHL9HU>

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elliottkember
I've been through this once. It was terrifying, and I wasn't even driving.
It's a good system, but frightening to behold.

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depsypher
I'm curious how one of google's self driving cars would fare on this.

