ADOT opens Diverging Diamond interchange I-17, Happy Valley Road

Construction will continue with lane restrictions this fall

PHOENIX – The state’s first major Diverging Diamond traffic interchange at Interstate 17 and Happy Valley Road in north Phoenix has opened to traffic, according to the Arizona Department of Transportation.

The design of the Diverging Diamond interchange includes intersections and traffic signals that allow drivers to cross and travel on the left side of the new bridge over I-17. In the Diverging Diamond, which has grown in popularity in several other states, motorists make direct left turns onto the freeway on-ramps rather than waiting to turn in front of traffic traveling in the opposite direction.

Construction is not yet completed at the Happy Valley Road interchange. The majority of the Diverging Diamond opened Sunday (Oct. 11) 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.

The reconstructed interchange allows for more lanes on the Happy Valley Road bridge, improved on- and off-ramps, fewer traffic-signal sequences and a reduction in conflict points for traffic. That enhances safety and allows improved traffic movement through the Diverging Diamond interchange. This past summer crews also removed the two roundabouts that had been in use at the interchange for the past two decades.

The I-17/Happy Valley Road interchange had been closed this weekend while crews installed signs as well as lane striping and other pavement markings.

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

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. 

This project was funded in part by Proposition 400, a dedicated sales tax approved by Maricopa County voters in 2004.