Do you know what to do if you’re in an accident?

The Arizona Department of Transportation is proposing construction of Arizona’s first diverging-diamond interchanges.

One of the interchanges would be built on Interstate 17 and Happy Valley Road. The other two would be built as part of the new South Mountain Freeway now under construction, which will extend the Loop 202 freeway from Chandler to Interstate 10 in west Phoenix.

ADOT officials said the design would create safer driving conditions by reducing the number of points where there are opposing directions of travel.

RELATED: Roundabouts on Arizona roads: Helpful or hurtful?

A diverging-diamond interchange is different from standard diamond interchanges in that local street traffic temporarily shifts to the left side while crossing the freeway, which allows for direct left turns onto entrance ramps without waiting for a traffic signal, ADOT said. 

The agency, in a news release, said the design “has been shown to enhance traffic flow while improving safety at busy interchanges” by reducing the number of points within an interchange where traffic crosses or merges. 

The agency construction of the diverging diamond interchange at Happy Valley Road would “have less of an impact on local businesses and commuters since traffic will continue to use the existing interchange while most of the construction work is taking place,” ADOT said in the news release. 

The project will replace the two roundabout intersections that have been at the Happy Valley Road interchange since 2001.

ADOT said it also plans to build diverging-diamond interchanges along the Loop 202 South Mountain Freeway, at Desert Foothills Parkway and 17th Avenue. 

If approved, the projects could begin in fall 2018.

The other ADOT project that hopes to curb wrong-way crashes


A dashboard-camera video from Kelly Knoll of Mesa shows him barely missing a wrong-way driver on July 4.

In June, the Arizona Transportation Board approved a $3.7 million plan to construct a thermal detection system to notify drivers and law enforcement when a wrong-way vehicle enters a freeway.

The system will be piloted on the Interstate 17 from the Interstate 10 to the Loop 101, ADOT said. 

Officials may explore expanding the system to other freeways in the Valley depending on the performance of the pilot system.

Nine people have been killed in wrong-way crashes in Arizona this year. 


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