Completed in April 2022, the $24.5-million diverging diamond interchange (DDI) at Houghton Road and I-10 is southern Arizona’s first and just the state’s second DDI. The interchange replaces the outdated 50-year-old two-lane bridge 15 miles southeast of Tucson. A lack of separate left turn lanes previously caused extensive delays during peak hour traffic, and the existing bridge was not capable of carrying the anticipated traffic growth on both the local road and the highway. The new interchange increases capacity from 8,000 vehicles daily to 50,000.
In a DDI configuration, each direction of Houghton Road traffic crosses to the left side over the freeway. This allows for left turns onto the on-ramps without waiting at a traffic signal or having to turn across traffic. A DDI allows traffic to proceed through the crossover intersections quickly and move on and off the freeway more efficiently. The Arizona Dept. of Transportation also expects the number and severity of crashes to drop.