PHOENIX — It has been a long time coming, but drivers in north Phoenix are now able to have a smoother commute after a new interchange at Interstate 17 and Happy Valley Road opened over the weekend.
This is due to the new “diverging diamond exchange,” a modern approach to traffic management design.
Arizona Department of Transportation spokesman Doug Nintzel said, “This is a much larger interchange, a lot more capacity compared to what we had out there.”
Before the new interchange, a pair of roundabouts at each end of the bridge managed traffic flow. They had been in service for two decades and were long overdue to be replaced.
“The one thing we heard from the drivers for the I-17 and Happy Valley Road interchange was they really wanted those roundabouts to go away,” he explained.
Two factors primarily contributed to the wait: First, it is no easy task keeping up with the area’s growth. Second, how officials prioritized funds generated from Proposition 404.
“It’s a dedicated half cent sales tax for transportation projects,” Nintzel said. “It doesn't all go into freeways. It is divided up where some of the money goes into local streets.”
Construction began back in 2018 and roundabouts were removed over the summer.
A traffic signal has been removed as well. Now a phased opening commences.
“What they’ll see is traffic moving through the interchange with the diverging diamonds design,” Nintzel said. “But there will still be some lane restrictions.”
The diverging diamonds design is the first of its kind in the state.
ADOT borrowed ideas from its counterparts in St. Louis and Chicago, two cities already using the modern approach.
“I think people are really going to notice the difference when everything is finished,” Nintzel said.
The project's completion is expected later this fall.
