Interstate 17 Black Canyon Freeway I-17 Happy Valley Road Diverging Diamond

Yes, it was 2020 but progress still made along Phoenix-area freeways

Yes, it was 2020 but progress still made along Phoenix-area freeways


Yes, it was 2020 but progress still made along Phoenix-area freeways

Yes, it was 2020 but progress still made along Phoenix-area freeways

By Doug Nintzel / ADOT Communications
December 31, 2020

You’re not alone if you’ve said, “I can’t wait for this year to be over.” Despite the challenges and disappointments of 2020, there are improvements along Phoenix-area freeways that were accomplished during the year by ADOT’s planners, designers, engineers, contractors and field personnel.

Among the largest steps forward with work to improve highway safety and the movement of today’s and future traffic was completion of the $72 million widening of Loop 101 (Price Freeway) in the area from Baseline Road, south of US 60, down to the Loop 202 Santan Freeway in Chandler. Crews completed the addition of a new lane in each direction, along with other improvements, in August. 

This particular project was moved up in regional transportation plans in order for the added traffic capacity to be in place before the upcoming I-10 Broadway Curve widening project stretching from the Loop 202 interchange in Chandler to the I-17 “Split” near Phoenix Sky Harbor International Airport. That’s because Loop 101 will serve as an important alternate route when I-10 construction closures are needed.

ADOT also completed the reconstruction of the neighboring I-17 interchanges at Happy Valley and Pinnacle Peak roads in north Phoenix. You may not live in that area and haven’t had a reason to check out the significant upgrades at both interchanges, which are just a mile apart along the Black Canyon Freeway. The $50 million project was completed in early December, although many of the improvements were in place earlier in the fall. The most notable change was construction of the state’s first major diverging diamond interchange at Happy Valley Road (smaller diverging diamonds also are in place along Loop 202 South Mountain Freeway). 

The diverging diamond design, which has grown in popularity across the U.S. for safety and traffic flow benefits, uses intersections and traffic signals to allow drivers to cross to the left side of the bridge over I-17 and thus make direct left turns to the freeway on-ramps without crossing in front of opposing traffic. The reduction in such “conflict points” is a primary safety improvement. 

Not to be overlooked is the expansion of the interchange at Pinnacle Peak Road, where drivers now have more lanes to cross over I-17 or make left turns. That’s already helping with the movement of rush hour traffic. Oh, and I-17 was also widened by a lane in each direction between the two improved interchanges.

Another project in our 2020 spotlight didn’t involve widening a freeway, although we wouldn’t blame some drivers if they thought that took place. It was actually an I-10 project completed in the spring that primarily focused on adjusting lane stripes and signs to create more traffic capacity in the area near the Loop 101 (Agua Fria Freeway) interchange in the West Valley. Along eastbound I-10, the changes provided two lanes, instead of just one, for traffic approaching the ramp to northbound Loop 101. The move reduced sudden lane changes and collisions in the area by increasing the amount of room for drivers to work with. Traffic flow also was improved along westbound I-10 with the extension of a right lane carrying vehicles through the Loop 101 interchange. The safety project was done in partnership with the Arizona Department of Public Safety and Maricopa Association of Governments, the Valley’s regional planning agency.

So it’s on to 2021 and other improvement projects, including completion of the Loop 101 (Pima Freeway) widening between I-17 and Pima Road/Princess Drive in the north Valley. We’ll keep you posted on what’s in store. Make it a safe New Year!