Thornton Interchange opens, U.S. 20 improvements now complete


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The following is a news release from the Idaho Transportation Department.

RIGBY — The Thornton Interchange officially opened today and traffic is now moving, finishing a series of projects that improve the safety of motorists on the stretch of U.S. 20 between Idaho Falls and Sugar City.

This large multi-project effort started in 2000. During the last 16 years, the Idaho Transportation Department (ITD) has replaced 18 dangerous intersections with seven interchanges. These interchanges allow safe entrance onto and exit off this 28-mile stretch of U.S. 20.

To date, these projects have allowed for a 115-percent increase in traffic while decreasing the rate of serious-injury crashes by 75 percent and cutting fatalities by more than half.

“These projects are a perfect example of how good engineering can save lives while also increasing mobility,” said ITD Director Brian Ness. “That, in turn, makes Idaho’s system of roads and bridges better for businesses to move products and give citizens safer access to more of our great state.”


Crews remove barricades to open the interchange to traffic Friday morning. | Idaho Department of Transportation

As with the previous construction projects, this replaces intersections of road that were at ground level. Those gave motorists little room to merge onto roads or cross the four-lane highway.

“Building interchanges and eliminating at-grade accesses minimizes points of conflict for through and local traffic, furthering safety and mobility for motorists,” said ITD District 6 Engineer Jason Minzghor.

“Completing the U.S. 20 corridor significantly improves the state highway system in eastern Idaho.”
Crews will continue to erect signs and fencing along the highway right of way. Final landscaping will be complete in the spring.

The total cost of all seven interchange projects (listed below) will be $85 million.

• St. Leon (Exit 311) – Completed in 2004-2005
• Hitt (Exit 313) – Completed in 2004-2005
• County Line (Exit 318) – Completed in 2001
• Menan-Lorenzo (Exit 325) – Completed in 2010-2011
• Thornton Interchange (Exit 328) – Completed in 2016-2017
• Sugar City-Salem (Exit 338) – Completed in 2001
• Driggs-Jackson (Exit 339) – Completed in 2001