

A new kind of interchange eliminates left turns. - brianmckenzie
http://www.slate.com/id/2300425/

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ColinWright
"New" ?? This was discussed 410 days ago::
<http://news.ycombinator.com/item?id=1437430>

Also just recently re-submitted: <http://news.ycombinator.com/item?id=2833446>

In particular, here's the WikiPedia article about the design:
<http://en.wikipedia.org/wiki/Diverging_diamond_interchange>

~~~
gojomo
New to most people; I haven't driven through one yet. And on the timescales of
road engineering, pretty much anything novel in the past 20 years that's not
yet widespread is still 'new'.

~~~
Semiapies
Also, the "new" is in the headline.

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psadauskas
They have something similar near the town I grew up:
[http://maps.google.com/maps?q=columbus,+in+&hl=en&ll...](http://maps.google.com/maps?q=columbus,+in+&hl=en&ll=39.200267,-85.957611&spn=0.006876,0.011244&sll=37.0625,-95.677068&sspn=56.768363,92.109375&t=h&z=17)

It was terrible the first few years. Nobody could ever figure out which lane
they were supposed to be in, and ended up driving on the wrong side of the
crossed-over section. Granted, the people here are still having trouble
figuring out roundabouts, but I found this very confusing my first couple
times through the intersection.

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chadgeidel
I live in a town of _spectacularly_ bad drivers so I may be jaded, but I just
can't believe folks will "figure this out". People where I live have a hard
enough time figuring out what lane they should be in on a straight two lane
road let alone merging, signalling, stopping at intersections, one-lane
roundabouts, etc.

~~~
treeface
You might think so, but everyone says this everywhere in the world. For
example, this is the top argument that people use against the implementation
of the generally-safer, higher-throughput modern roundabouts. Without fail,
every time a modern roundabout is installed, the exact same thing happens:
congestion is eased, the incidence of fatal accidents falls some 90%, and a
multitude of people say things like "well, I just couldn't believe that these
people where I live were smart enough to handle it, but it worked!"

What people usually attribute to bad driving is usually the fault of poor
traffic planning. Humans tend to be the same, circumstances change.

~~~
asmithmd1
Massachusetts has the worst drivers in the the country - that is a fact - MA
has the highest accident rate in the US. I blame the roads. Every intersection
in MA is unique - there are no idioms. Take a look at these two intersections
with 4 lane roads that were recently "fixed"

Just keep moving or you will be stuck for hours:
[http://maps.google.com/?ll=42.361501,-71.070455&spn=0.00...](http://maps.google.com/?ll=42.361501,-71.070455&spn=0.002426,0.004823&t=k&z=18)

Something for everyone: overpass, circle, and jug handles:

[http://maps.google.com/?ll=42.24915,-71.171166&spn=0.002...](http://maps.google.com/?ll=42.24915,-71.171166&spn=0.00243,0.004823&t=k&z=18)

~~~
treeface
_Massachusetts has the worst drivers in the the country - that is a fact - MA
has the highest accident rate in the US._

A high accident rate is not proof that Massachusetts "has the worst drivers in
the country". I've lived in Massachusetts (and New Jersey, California, and a
bunch of other places that like to call themselves the "worst drivers"), but
everywhere I go, it seems apparent to me that road conditions and layout
account for the huge majority of deviations from place to place.

For example, in New Jersey there are a ton of highways that don't have onramps
(or about 15 feet of it). Because of this, there are a lot more (I mean a LOT
more) collisions on the "onramp" and people generally are used to swerving in
front of 65-mph traffic from a complete stop.

In California you have just as many people (or maybe more) who swerve in and
out of lanes at unreasonable speeds, but since there are so many lanes and
since they're all so fantastically wide, that sort of behavior doesn't get
punished as it might, say, on the Mass Pike or the Garden State Parkway. At
the same time, city roads in California (at least in OC) tend to have much
higher speed limits. This causes a marked increase in fatal collisions at
these types of intersections...not because the people are inherently more
aggressive, but because the roads shape their behavior.

~~~
cafard
I have often thought that the state seal of Pennsylvania should include a stop
sign at the end of an on-ramp. It also has a way letting bridge abutments jut
about halfway out into a lane so that the merge and exit lanes are divided.

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m0nastic
I didn't get very much sleep last night, but it seems like a more complicated
solution than just using "jug handles".

~~~
matwood
I'm glad someone brought this up. I think it's NJ that has a lot of jug
handles and they do a pretty good job at eliminating all left hand turns and
once I understood the term they were easy to use. I also think they would be
easier to implement on existing roads.

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protomyth
I cannot help but think this thing will be a nightmare in the snow. It just
has a slide into the wrong place vibe.

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juiceandjuice
They started putting in lots of continuous flow intersections in Utah:
<http://en.wikipedia.org/wiki/Continuous-flow_intersection>

~~~
vyrotek
The new Pioneer Crossing intersection is great. I drive through it every day.

Here's a video describing the flow:
<http://www.youtube.com/watch?v=xWHEi8baCPE>

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oflannabhra
They're in the process of building one of these here in Lexington, KY. The
link the the video simulation was definitely enlightening. We'll see whether
drivers will actually be able to pick up how to navigate it.

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Bo102010
There is one of these 300 meters from my apartment.

It's not very confusing exiting the highway and turning left - just follow the
lights.

It is kind of confusing exiting the highway and turning right. Right-on-red is
allowed, and to make such a maneuver you have to look in strange places for
traffic that might hit you. I've almost messed it up a few times. The other
option is to let people honk at you while you wait for a green.

I'm curious as to what will happen when the power to the lights fails.

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murz
Reminds me of Michigan left.

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

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pedalpete
isn't each point of cross-over/merging a more likely point of failure?

I could see there being less accidents of the left-turn variety being
exchanged for more less-dramatic accidents.

Aren't we better of just using roundabouts? or
<http://en.wikipedia.org/wiki/Roundabout#Turbo_roundabouts?>?

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digitalstax
I lived a few blocks from the one in Springfield, MO when it was built. It
just doesn't feel right at first. But I haven't heard of any problems and it
seems to serve its purpose.

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savrajsingh
You mean a roundabout?

