By Les Conklin
Scottsdale’s new traffic circle features “Aspire” by Simon Deckert and Ben Olmstead. Photo by Sean Deckert. Courtesy of Scottsdale Public Art.
Despite dire warnings of traffic jams, stock-car-race-like sideswipes, rollovers and smashups, and predictions of the end of our driving world as we know it, it appears that Scottsdale has benefitted from the installation of a traffic circle on Hayden Road and Northsight Boulevard. While navigating the circle I can’t say that I’m able to enjoy the centerpiece art (see photo to right), but the traffic does move more efficiently. Congratulations!
This is my question. Now that we’ve mastered the traffic circle, how would residents react if the city proposed a diverging diamond Interchange for a road that intersects with the Loop 101?
First Encounter
Last summer, my wife and I were headed for the recreation center in Louisville, Colorado, which is near our son’s home in Superior, Colorado. As we got in our car, our son informed us that construction had just been completed on improvements to a major traffic intersection on our route. He told us to follow the signs, stay calm, and “take the center lane” to get to our destination.
We did not know it at the time but we were about to have our first encounter with a diverging diamond interchange. The encounter was a bit nerve-racking, but when it was over, I could not help but smile and wonder how critics of Scottsdale’s Hayden-Northsight traffic circle would react to the diverging diamond driving experience.
Diverging Diamond?
A diverging diamond interchange is designed to facilitate traffic flow where a major highway, like the Loop 101, with traffic entering and exiting in both directions, intersects with a major road. I’m not a civil engineer, so I am going to punt my writing responsibility and leave it to Wikipedia to define a diverging diamond interchange.
Conceptual Diagram of Louisville-Superior Diverging Diamond Interchange. Courtesy Superior, CO.
“A diverging diamond interchange (DDI), also called a double crossover diamond interchange (DCD), is a type of diamond interchange in which the two directions of traffic on the non-freeway road cross to the opposite side on both sides of the bridge at the freeway. It is unusual in that it requires traffic on the freeway overpass (or underpass) to briefly drive on the opposite side of the road from what is customary for the jurisdiction. The diverging diamond interchange was listed by Popular Science magazine as one of the best innovations in 2009 (engineering category) …”
In Superior, the new interchange at McCaslin Boulevard and U.S. 36 is a major improvement over the old approach, which required many traffic lights, many turning cars, stops, starts, etc., but don’t get me wrong. I hope Scottsdale does not need a diverging diamond any time soon. My point is that if people were concerned about a traffic circle at Hayden and Northsight, when traffic circles have been employed elsewhere for many, many years, then those folks need to be aware that there is an idea from 2009 that might be coming down the road.
Related Websites
Official Website of Diverging Diamond Interchanges, http://divergingdiamond.com/
Superior, Colorado Department of Public Works, http://superiorcolorado.gov/departments/public-works-utilities/streets/divering-diamond-interchange
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