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Video visualization of a new type of traffic-improving intersection

By Rain Noe - October 28, 2010

in Tech

When I used to have a car in Manhattan I considered myself an expert at navigating the traffic sprawl, as I knew the city like the back of my hand and could usually work my little five-speed VW to the front of any pack. I'd often joke to my friends that Manhattan, due to all the one-way streets and congestion, was a place where you could often get to your destination faster by initially moving in the opposite direction. (No one ever laughed.)

The concept of going the wrong way to reduce overall trip duration can also be seen in the "diverging diamond interchange," a new (to the U.S.) form of highway intersection that reduces "conflict points" by asking drivers to temporarily switch to the "wrong" side of the road. It's kind of complicated, but see if you can follow along:

...The diverging diamond interchange allows for two-phase operation at all signalized intersections within the interchange. This is a significant improvement in safety, since no left turns must clear opposing traffic and all movements are discrete, with most controlled by traffic signals.

Additionally, the design can improve the efficiency of an interchange, as the lost time for various phases in the cycle can be redistributed as green time; there are only two clearance intervals (the time for traffic signals to change from green to yellow to red) instead of the six or more found in other interchange designs.

Still confused? Perhaps this visualization will help, where the little intersecting red lines signify traffic lights:

Pioneered in France, the first U.S. diverging diamond interchange was constructed last year in Springfield, Missouri.

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GenMX

13 years ago

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Hi, I enjoyed your post while I was reading this but I want to know more about it.
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Anthony

13 years ago

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Echoing what Britt said, the new interchange in American Fork Utah has saved me a good chunk of time in my daily commute. The lights are very fast and there's always a flow of traffic.
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Adam

13 years ago

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What's wrong with a good old clover-leaf intersection?
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Britt

13 years ago

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They just completed construction and opened up one of these in American Fork, UT. They're great and offer shorter traffic lights and more continuous flow of traffic which is great! There is absolutely no problem when 'switching' sides of the road. You can't even tell you're on the left side. IT looks kind of confusing from a bird's eye view, but at street level, it's just like anything else in my opinion.

The impressive thing was seeing them build the bridges on the side of the freeway and them move them into place with massive equipment!
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Ray Jepson

13 years ago

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When will we finally admit the failure of controlled intersections and just accept that round-abouts are the ideal.

It was so refreshing to drive in Spain because of this.
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matthiasr

13 years ago

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Here's how they build Autobahn (Freeway) crossings in Germany:

http://de.wikipedia.org/w/index.php?title=Datei:AK-Kleeblatt.svg (from Wikipedia)

There are no traffic lights at all, and traffic can flow freely in any direction. Those changing direction have to give way upon entering the new Autobahn, but long acceleration lines make it possible to match speed and simply join the flow. It is also customary for those already on it to free the right lane around such entry points whenever traffic admits it.
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Wouter Walmink

13 years ago

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At first, I thought "great, what a refreshing idea!".
But on second thought, there seem to be two catches here:

1.
The advantage of having only 2 steps in the traffic light cycle is not caused by the switching of lanes. It's rather the fact that one road is going over the perpendicular road, reducing 2 traffic lights in the cycle. If you would not switch lanes, two steps would still do, as long as you have the "going right" before the cross section and the "going left" after.

2.
Those going left will have to give way to the folks on the freeway, which might mean some waiting during busy times. Though probably manageable most of the time, a long line at one of the ramps for going left would cause the traffic from the other direction to be blocked. This problem also goes for a traditional no-switching solution.

All in all, it doesn't seem to bring much advantage over the old system?
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Brent A.

13 years ago

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I grew up in Springfield and saw this on my last trip back when I was visiting family. For the traffic going straight through the interchange, there are the same amount of lights, but you don't have to wait for cars turning left onto the freeway. It does considerably save time from that perspective. When you are coming off the freeway into the intersection, you no longer have to sit through two lights, which is normally the case. Instead you can turn left or right immediately after yielding, and only sit through one light (if you are turning left).

I've always thought Springfield's traffic patterns are above par. For example, if you start at Glenstone and Kansas Expressway with a green light, you can basically get 80% of the way across town before hitting a red light at Sunshine. The first time I went to the northeast, I felt like I was hitting every single red light, but major roads in Springfield seemed to be timed about right in relation to one another.
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William Sutton

13 years ago

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Why not just elevate one lane over the other where they have the traffic light? Then no one even has to stop.
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Matt M

13 years ago

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Here is a visual of the one in Springfield, MO: http://goo.gl/maps/WRfx
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-Joel-Kramka-

13 years ago

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I could be wrong but this doesn't seem faster than most interchanges because you still have to wait for the lights to change. It also doesn't leave much room for error if there is a lot of traffic backed up. The individual lanes to turn right of the interstate are a good Idea so that people don't really have to stop but overall this doesn't really solve the congestion problem.

As far as the safety issue goes. I get that you don't turn left into oncoming traffic however, I could be wrong but most accidents seem to happen in this manner when someone goes through a red light or tries to speed through a yellow. This will not solve that, in fact it will cause the collisions to be both cars head on.

Idno about this one in particular but I like that someones looking for better Ideas in this field.
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Ahmad

13 years ago

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what not bridge the huge 2 intersections? one in top of the other on both ends?
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djreno

13 years ago

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I drove through the Springfield intersection while on a road trip. There is a serious WTF moment involved in switching to the "wrong" side of the road, but then its over and I was on my merry way.
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djreno

13 years ago

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I drove through the Springfield intersection while on a road trip. There is a serious WTF moment involved in switching to the "wrong" side of the road, but then its over and I was on my merry way.
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