Gallery: Keystone Parkway Is the Greenest Highway Intersection in the U...


The suburban city of Carmel, Indiana has built a double teardrop roundabout that could very well be the greenest highway intersection in the United States. It’s a compelling solution to the various challenges the city faced when they needed a major upgrade to one of their busiest intersections. The unique solution has saved many buildings, reduced accidents dramatically, reduces carbon emissions and is much more pedestrian friendly — all the while saving the city money as compared to a traditional highway intersection.  While America’s devotion to cars will not wane anytime soon, maybe America’s roads can get a bit better at reducing the automobile’s impact.

Photo © Ubanophile

Carmel, a suburb of Indianapolis, is the undisputed roundabout capital of the country with a total of 65 and more to come. One of the most clogged intersections, now called the Keystone Parkway, was due for a redesign, but due to the amount of development around the crossing, even very tight traditional highway onramps would have meant the removal of a number of existing buildings. Naturally, the city looked at how a roundabout could be used to improve the traffic flow and reduce accidents without gobbling up so much occupied land.

The breakthrough design uses 1/3 less area than the tightest traditional diamond intersection, preserving dozens of buildings and significantly reducing traffic noise. The design also eliminates stoplights which reduces car idling and improves traffic flow while slowing them down and reducing accidents by a staggering 78%. The intersection adds green space and provides a much more pedestrian and bike friendly crossing, with street lighting and wide egress.

The design and construction firm American Structurepiont had to model the project in Autodesk’s 3ds Max software to simulate the driving experience to make sure the concept was going to work in the real world. They also used the simulations to convince the city that the $112 million was money well invested, saving the city $1 million in construction costs compared to traditional designs.

+ American Structurepiont

Via Autodesk AEC


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1 Comment

  1. skippypt May 12, 2011 at 8:56 am

    I’d love to see the truck turning movements, a traditional left looks difficult for a semi. Great looking alternative though!

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