WEST DES MOINES, Iowa – A project that has been in the works for almost 15 years will open Tuesday afternoon. The Grand Prairie Parkway interchange is the first-of-its-kind in Iowa. It’s called a diverging diamond interchange.
“The big things with this intersection are it’s more efficient, it’s safer and it has a smaller green footprint,” said traffic engineer Eric Peterson with the City of West Des Moines.
The cities of Waukee and West Des Moines, along with the Iowa Department of Transportation will open the Grand Prairie Parkway Interchange and the roadway leading into Waukee. The Iowa DOT will open the interchange to the public at 12 p.m.
Construction on the roadway kicked off in November 2013 and work began on the interchange portion in November 2014. The total cost of the project to date is $50 million, with funding provided by a variety of federal, state, and local revenue sources.
The opening of the Grand Prairie Parkway Interchange will provide great relief to other major interchanges and arterial routes in the western metro area including Jordan Creek Parkway, University Avenue, and Hickman Road. Officials predict that from day one, 12,000 drivers will utilize Grand Prairie Parkway.
The diverging diamond design is well-known in other parts of the country for improving the safety of traffic entering interstate systems and allowing for increased vehicle capacity and reductions in time delays.
A typical diamond interchange has 26 potential conflict points. A diverging diamond interchange (DDI) has 14 potential conflict points. This reduction is primarily due to removing the right-angle conflicts where left-turning drivers must yield to oncoming traffic.
Iowa DOT collaborated with the Missouri Department of Transportation to analyze crash data. Missouri currently has a handful of similar interchanges. The crash data for interchanges that were converted from a typical diamond interchange to a DDI showed an average crash reduction of 35%. Compared to a typical diamond interchange: with increased capacity 15-25%. The researched also showed that Missouri saw a reduction in delay time at high volumes by 60%.
“This new road will have an immense impact on traffic flow in the Waukee area and beyond. For years, western metro residents have needed a more direct route to I-80, and after much planning and hard work, it’s becoming a reality,” said Waukee Mayor Bill Peard. “Not only does it bring better access to drivers, but it will also open the door to residential, office and commercial development for Waukee’s new Kettlestone Development.”