Diverging Diamond interchange opens soon at I-17 and Happy Valley Road

The I-17 interchange at Happy Valley Road in north Phoenix will have the state’s first full diverging interchange, like this one found in Washington State. It is scheduled to open to traffic on Sunday, Oct. 11.

Design promotes safety, improved traffic movement

Contributed Article/Courtesy ADOT

PHOENIX – The state’s first major Diverging Diamond traffic interchange at Interstate 17 and Happy Valley Road in north Phoenix is scheduled to open to traffic on Sunday, Oct. 11, according to the Arizona Department of Transportation (ADOT).

The majority of the reconstructed interchange will open in a temporary configuration as part of a phased plan. Some lane restrictions will be in place on Happy Valley Road and the I-17 exit ramps until all work is completed later this fall. Drivers can look forward to using a modernized interchange with more lanes on the new bridge crossing over the freeway. 

The Diverging Diamond interchange design, which has grown in popularity across the country, includes intersections and traffic signals that will allow drivers to cross to the left side of the Happy Valley Road bridge over I-17. That switch means motorists can make direct turns onto the freeway entrance ramps rather than waiting to turn in front of traffic traveling in the opposite direction.

A reduction in such conflict points and fewer traffic-signal sequences are safety enhancements that also allow an improved movement of vehicles through the Diverging Diamond interchange.

All I-17 on- and off-ramps at Happy Valley Road will be closed from 9 p.m. Friday to 5 p.m. Sunday. Happy Valley Road also will be closed in both directions approaching I-17.

ADOT is nearing completion on a $50 million project to reconstruct the I-17 interchanges at Happy Valley Road and Pinnacle Peak Road. The section of I-17 between Happy Valley and Pinnacle Peak roads also has been widened by one lane in each direction. Work on the project started in November 2018.

Crews have been able to maintain traffic along Happy Valley Road during most of the interchange reconstruction. The Diverging Diamond interchange project also allowed crews to remove the two roundabouts that had been in use at the Happy Valley Road interchange for the past two decades.

In addition to the improved Happy Valley Road interchange, crews also have reconstructed the I-17 interchange one mile south at Pinnacle Peak Road. It is being expanded as a traditional diamond interchange featuring more lanes and turn bays on the bridge over I-17. Construction at I-17 and Pinnacle Peak Road also is scheduled to be completed later this fall. 

ADOT’s project was funded as part of the Regional Transportation Plan approved by Maricopa County voters in 2004.