The end of the line is nearing for the roundabouts at the Interstate 17 interchange at Happy Valley Road in north Phoenix.

The Arizona Department of Transportation will soon replace the roundabouts as part of an ongoing project to add the state’s first full diverging diamond interchange. A traffic switch away from the roundabouts is expected to take place in the coming weeks, according to a release.

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.

When the roundabouts are replaced, 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, according to the release, thus enhancing 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, the release states.

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.