End of the line for roundabouts at I-17, Happy Valley Road

It’s the end of the line for the roundabouts at the Interstate 17 interchange at Happy Valley Road in north Phoenix. The Arizona Department of Transportation is replacing the roundabouts starting this weekend (Aug. 7-10) as part of an ongoing project to add the state’s first full diverging diamond interchange.

The Happy Valley Road roundabouts have been in use for the past two decades to help move traffic through the freeway interchange. ADOT’s $50 million project provided funding to add a larger bridge over I-17 for the diverging diamond interchange designed to enhance safety and improve traffic flow. The project is scheduled for completion this fall.

With the removal of the roundabouts, crews will focus on completing on- and off-ramps that connect to the diverging diamond interchange at Happy Valley Road.

The diverging diamond design includes intersections that allow traffic to cross and use the left side of the Happy Valley Road bridge over I-17. That improves traffic flow by limiting traffic signal changes and allowing drivers to make direct left turns to enter freeway on-ramps without crossing in front of opposing traffic. That enhances safety by reducing conflict points for traffic.

Diverging diamond interchange design has grown in popularity across the country because of the traffic and safety benefits.

All I-17 on- and off-ramps at Happy Valley Road will be closed from 9 p.m. Friday night to 5 a.m. Monday, Aug. 10, for removal of the roundabouts and installation of temporary traffic signals. Happy Valley Road also will be closed in both directions over the weekend. The following 60-day closures will remain in place while construction continues:

  • Southbound I-17 off-ramp at Happy Valley Road closed. Southbound I-17 frontage road between Jomax and Happy Valley roads closed. DETOUR: Drivers should consider exiting to eastbound Jomax Road and using southbound 19th Avenue to westbound Happy Valley Road while the southbound off-ramp is closed. Drivers also will have the option of exiting to westbound Pinnacle Peak Road and using alternate routes, including northbound 43rd Avenue, to reach Happy Valley Road.
  • Northbound I-17 on-ramp at Happy Valley Road closed. Northbound I-17 frontage road also closed between Happy Valley Road and Agave. DETOUR: Drivers should consider using northbound 19th Avenue to westbound Jomax Road to reach northbound I-17.

ADOT’s project also is reconstructing the interchange at Pinnacle Peak Road and adding new lanes in both directions along I-17 between Pinnacle Peak and Happy Valley roads.

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