Work on 1st Avenue 'diverging diamond' interchange will close westbound exit ramp through June
Road work ahead.
Beginning Tuesday, April 2, the 1st Avenue exit onto Interstate 80 westbound will be closed for nearly three months as construction crews continue work on a "diverging diamond" transformation.
The westbound on-ramp will be closed through mid-June, the Iowa Department of Transportation estimates. Changes have already been made to the other three on and off-ramps.
Signs will detour drivers eastbound to Dubuque Street and funnel them around that intersection to the westbound interstate on-ramp.
Meanwhile, the "fully completed" I-80 off-ramp for eastbound travel will open on April 2. For months, ongoing construction had significantly narrowed that exit.
The Coralville interchange at 1st Avenue 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 interchange began in March 2023.
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Project still set to complete by end of year
The $42 million Iowa Department of Transportation project is using an interchange design model that the department says improves safety and reduces traffic delays by eliminating turns across oncoming traffic for cars entering and leaving the highway.
The project will be completed by the end of 2024, less than two years after it began. It will transform the entire area, creating a "diverging diamond" interchange.
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What is a diverging diamond interchange?
The benefits of a diverging diamond interchange, according to the Iowa DOT, provide left turn “movements that are unopposed,” while the layout also improves “signal timing” and shorter traffic signal cycles. Diverging diamond interchanges allow for free-flowing turns when entering or leaving the interstate, according to the Department of Transportation, by eliminating left-hand turns across oncoming traffic.
This is accomplished by developing lanes that cross to the opposite side of the interchange.
A diverging diamond is meant to "reduce traffic" delay and improve safety by eliminating the left turn across traffic.
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New, southbound overpass work continues
Crews are currently constructing a new bridge that crosses I-80 for southbound traffic, part of the two-bridge setup of the diverging diamond. A separate pedestrian pathway on the east side of 1st Avenue opened late last year and includes a new trail over the interstate.
On the east side of 1st Ave, traffic is limited to one lane in each direction while the new southbound bridge is being built.
The City of Coralville said that while the trail underpass is nearly complete, more work on the northwest side of the interchange remains, which will keep that trail segment closed. According to the city's website, bike riders, walkers, and joggers are instructed to use a temporary sidewalk on the east side of 1st Avenue "between the westbound I-80 off-ramp and the River Products driveway."
The City of Coralville also said the new interchange bridges are being built to accommodate future interstate widening.
In February, the Iowa DOT, which is leading the project, reported that the interchange project was more than 60% complete and "all permanent lanes and trail improvements" will be open to the public by the end of this year.
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: Coralville's 'diverging diamond' project will close I-80 westbound exit
