Diverging diamond traffic pattern debuts at 1st Avenue interchange. Here's how it'll work:
Traffic safety should be vastly improved near the Iowa River Landing in Coralville.
The new "diverging diamond" interchange along 1st Avenue near Interstate 80 exit 242 will open Thursday, May 23, initiating a key moment in the roughly 18-month construction project, which began last March.
In diverging diamonds, drivers are directed to the opposite side of the road near on- and off-ramps. The Iowa Department of Transportation said the design "eliminates conflicts where traffic crosses," reducing the likelihood of collisions while providing a more efficient means of navigation.
This is because, for example, drivers exiting the highway and turning left need only pull into the closest lane rather than crossing traffic.
The Coralville interchange at 1st Avenue (between 9th Street and Holiday Road) is one of the busiest in the Iowa City metro area, leading to the heart of Coralville, the Iowa River Landing and Xtream Arena to the south, and residential areas to the north.
Work on the $42 million Iowa Department of Transportation interchange project began in March 2023 and is 75 percent complete, according to the City of Coralville.
More: Work on 1st Avenue 'diverging diamond' interchange will close westbound exit ramp through June
Navigating a new interchange
The new interchange will impact all traffic, not just cars entering and exiting the highway. Vehicles heading north and south along 1st Avenue will also cross onto the opposite side of the road.
For example, a southbound driver approaching from the 1st Avenue roundabout headed for the Iowa River Landing would approach in the west lane of the road, then cross I-80 on the east side of the road and return back to the west lane after traveling through the interchange.
Traffic signals, pavement markings and signage will help drivers adjust to the new configuration, the city said in a release.
Throughout the summer, 1st Avenue will operate as a single lane in both directions but will transition to two lanes once construction is complete.
More: Meet the latest nominees for the Press-Citizen's Student of the Week
Westbound on-ramp reopened ahead of schedule
The westbound I-80 on-ramp, which has been closed since April 2, will also reopen Thursday.
Drivers have been detoured one full exit east to Dubuque Street and funneled around to head west. The project has reconstructed each of the four on- and off-ramps.
Pedestrians and cyclists will continue to use the newly-opened tunnels and a trail bridge over the interstate.
Construction will continue through the summer as crews put the finishing touches on the project. All work is expected to be completed by the fall.
More: ACT Inc. transitioning to a for-profit business focused on 'financial and social impact'
Diverging diamonds in Iowa
Diverging diamonds are a relatively new concept. The first such interchange in Iowa was installed in Ankeny in 2015. One year later, an accident near the interchange involving a drunk driver sparked a lawsuit that blamed the diverging diamond configuration for the incident, the Register reports.
Ryan Hansen covers local government and crime for the Press-Citizen. He can be reached at [email protected] or on X, formerly known as Twitter, @ryanhansen01.
This article originally appeared on Iowa City Press-Citizen: How will Coralville's diverging diamond interchange work?
