JEFFERSON CITY - Driving on the wrong side of the road may not seem like a logical way to design a highway interchange, but that's the concept behind a new intersection in southwest Missouri that Popular Science magazine has named one of its 100 best innovations of the year. Each year, the science and technology news magazine picks the best of what's new, including "the 100 fastest, biggest, safest, greenest and most powerful innovations of the year."
One of those is a highway interchange located near Springfield, Mo. at Route 13 and Interstate 44 that uses a diverging diamond configuration to move traffic through the intersection. With the diverging diamond design, the opposing lanes of traffic crisscross at traffic signals.
Crossing the bridge, oncoming traffic is on the right, separated by concrete barriers and screening. This gives left-turning vehicles a "free left" onto the intersecting roadway. At the same time, traffic continuing north or south is able to travel more steadily through the interchange. Signs, pavement markings and concrete islands clearly guide drivers and help prevent making a wrong turn into the opposing lanes.
According to Popular Science, the Federal Highway Administration estimates that the diverging diamond configuration enables 600 left turns onto the freeway per hour per lane - double that of an ordinary interchange where drivers cross oncoming traffic.
The design has been used in Europe, but the Springfield interchange is the first of its kind in the United States. It opened to traffic in June and has been successful in moving more traffic in less time through the busy northwest gateway to Springfield. The Missouri Department of Transportation has plans to build similar interchanges in the Kansas City and St. Louis areas.
The Popular Science article can be found at http://www.popsci.com/bown/2009/product/diverging-diamond-interchange, and more information on the diverging diamond concept, including an animation, is located at http://www.modot.mo.gov/springfield/major_projects/Greene/I-44andRoute13.html.
In addition, there are two videos available on YouTube showing how the diverging diamond interchange works. You can view them at http://www.youtube.com/watch?v=B5JtZMPTNAY and http://www.youtube.com/watch?v=NANacKPO0Q4.
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