About the Project
Arizona’s Second Diverging Diamond Interchange Significantly Increases Capacity
Tucson’s new diverging diamond interchange (DDI) at Interstate 10 and Houghton Road increases daily capacity from 8,000 vehicles per day to 50,000. The $24.4-million interchange, the first DDI in southern Arizona and just the second of its kind in Arizona, replaced a 50-year-old outdated two-lane bridge. In the DDI configuration, each direction of Houghton Road traffic crosses to the left side over the freeway, allowing for left turns onto the onramps without waiting at an additional traffic signal or having to turn across traffic. The DDI was selected over other options because it has fewer conflict points, particularly in left turn movements, making it one of the safest options. It also had lower construction costs, lower right-of-way impacts and the highest traffic accommodation. Stanley Consultants led the study concept, final design and post design.