Happy Valley Road Traffic Interchange
The scope of work includes:
- Removing the existing roundabouts and constructing a new traffic interchange. A Diverging Diamond traffic interchange is planned for this location.
- Constructing a new underpass bridge that would accommodate potential future expansion of I-17
- Reconstructing Happy Valley Road to three through lanes in each direction with right- and left-turn lanes as needed
- Re-grading the detention basins
- Installing Freeway Management System signage, ramp meters, signals, lighting and pavement markers
- Re-seeding areas disturbed by construction
Construction at both interchange locations is anticipated to occur within existing ADOT right-of-way.
The Diverging Diamond Interchange (DDI)
A DDI is a diamond interchange on which the two directions of traffic on the cross street (above or below the freeway) cross to the opposite side on both sides of the bridge at the freeway. In the United States, more than 80 DDIs have been constructed in 29 states since 2009. The design has increased in popularity because of safety, operational and cost benefits. DDIs can reduce the number and severity of crashes compared to traditional diamond interchanges, while reducing traffic congestion. They also provide an excellent opportunity to integrate multimodal facilities for pedestrians, cyclists and transit into the interchange. They can be more cost effective to build, and there are fewer impacts on the local community during the construction process.
If you’re curious to see how a DDI works, watch this video from the Illinois Department of Transportation (IDOT). Recently IDOT constructed a DDI at I-88 and Route 59 near Chicago. This DDI’s design is similar to what is being planned for I-17 and Happy Valley Road.