CORALVILLE — The driver doesn’t have to be in a semi-trailer truck to feel the pull of the tight turn on the Interstate 380/80 interchange in Johnson County, but it’s the truck drivers who are most likely to face the danger.
The interchange is identified in a new American Transportation Research Institute report as the worst heavy truck rollover “hot spot” in Iowa. Thirty heavy trucks rolled over at the interchange during a study from 2001 through 2009, more than any other spot in the state. Rollover accidents averaged 346 annually in Iowa over the nine-year study.
A solution is in sight for the interchange, but it’s a long way off.
The Corridor Metropolitan Planning Organization of Johnson County will vote May 23 on a new long-range transportation plan that includes a new interchange that addresses design flaws that are the underlying issue contributing to the rollovers.
Johnson County Sheriff Lonny Pulkrabek said the turning radius “seems to get tighter the higher you go into the curves, and the truck’s load will shift or the rear end of the truck will slip out.”
“It’s one of the most troublesome cloverleafs in the United States in my opinion,” Pulkrabek said.
In addition to its tight turning radius, the interchange has only one “merge/diverge” lane for I-80 traffic entering and exiting to I-380 that often causes accidents of a less serious nature, according to transportation planner and Executive Director John Yapp of the planning agency.
Having the project in the agency’s plan will enable the Federal Highway Administration to conduct a interchange justification report that will determine if the reconstruction is warranted.
There is a lot to justify in this case, because the price tag for the new interchange is more than $300 million, and the federal government will have to shoulder most of the load.
The planning organization doesn’t see the money shaking out any time soon. The anticipated time frame for the project is 10 to 15 years, Yapp said.
“It’s by far the most expensive project in the plan,” Yapp said.
Cathy Cutler, regional planner for the Iowa Department of Transportation, said the highway administration has already approved an environmental assessment for the interchange replacement, and a preliminary design for a new interchange is completed.
The new design would alleviate the merge/diverge problem and create more-relaxed turning radiuses that would ease rollovers. Also, bridges would separate all the on- and off-ramp pavement to eliminate conflicts caused by merging traffic.
The huge expense of the project is due mainly to the need for the four bridges, Cutler said, although the project would also require the purchase of more land and the construction of more drainage structures.
The I-380/80 interchange dates back to the construction of I-380 as a four-lane interstate north of I-80 around 1970, and the reconstruction of Highway 218 to a four-lane divided freeway south of I-80 in 1982.
The project is not on the Iowa Department of Transportation’s draft 2013-2017 Transportation Improvement Program that was posted for public review Tuesday because the interchange justification report has not been completed.
In the meantime, the American Transportation Research Institute is using data from the rollover study to develop a satellite-based mobile communications network to alert drivers about the hot spots, said Rebecca Brewster, president of the non-profit research organization.