After three deaths and 80 accidents, Thornton Interchange to become an overpass
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REXBURG — After more than a decade of planning, the Idaho Transportation Department plans to start construction on the Thornton Interchange on March 1.
The work will set the state back around $14 million, but the hope is that it will improve traffic flows and, above all, safety. ITD plans to finish the project within 300 days of starting it.
The dangerous interchange has caused for numerous crashes, injuries and deaths. ITD believes that much of that is caused by adjoining roads being at the same level — or at-grade — to the neighboring highway.
If the intersection were given a grade, it wouldn’t pass, ITD Traffic Engineer Ben Burke said.
“It would get an ‘F.’ Right now, it’s at very low levels of service. The through traffic is so heavy; you can’t find a gap to get out,” he said.
Vehicles — most often large trucks pulling trailers — at a dead stop, have to immediately accelerate to 65 miles per hour to cross Highway 20. This situation proves dangerous and at times fatal, Burke said.
“There was a fatality the day the project bid opened for construction. A man from Utah was trying to cross and failed to see a semi — which is tough to do. He was broadsided,” he said.
In all, there were three fatalities in 2015. Yet, between 2011 and 2014, the interchange experienced no fatalities. It did, however, have its fair share of accidents and injuries.
From 1997 through 2014, ITD reported the interchange experiencing 80 crashes, involving 131 vehicles and 217 people. Of those people, 144 were injured.
“A lot of them are single vehicle slide offs. It gets slick, they slide off and crash. They’ll fall into a ditch,” Burke said. “Ice contributes. Drivers are speeding or going too fast for conditions. It’s posted at 65. They should be going 45. It’s just too slick.”
It’s hoped that the new overpass will help eliminate many of the crashes.
“There’s four intersections through there. We plan to close all four intersections and just have the one interchange. U.S. 20 will go up over the top,” he said. A county road will run underneath.
This venture proves a mammoth one for the state, Burke said.
“It’s one of our larger projects. We usually don’t have projects that big,” he said.
The Thornton project has been in the works since 2001. Burke is the first to agree that it’s taken some time to get it done.
“We had to decide where to put it, open paths and hold public hearings — all that good stuff,” he said.
The work also included removing power lines, purchasing right of ways and private property. It also required environmental and economic studies.
Numerous public hearings were held to address the economic impact. During one such event, Yellowstone Bear World officials voiced concern that the new overpass would negatively impact business.
“At this point, we are quite concerned that once they build that overpass we stand to lose tourism in the region,” Ferguson said during one meeting reported on by the Standard Journal. “By my records, I stand to lose at least 40-50 percent of my business.”
While officials said that another off ramp near 4300 south will direct tourists to Bear World, Ferguson was still concerned visitors would have to drive two miles out of their way to get to the park.
Burke said that ITD knows there are a few businesses along the route, but says that owners have generally been supportive of the changes.
“I think they’re welcoming the interchange. It’s making it safer to get across,” he said.
ITD built the original Thornton Interchange during the late 1970s or early 1980s. It’s anybody’s guess why safer overpasses weren’t built as well, but in recent years, ITD has increased safety by closing interchanges on Menan, Lorenzo, Hitt and St. Leon Roads.
“We’ve closed at-grade roads and put in overpasses,” he said. “The Thornton is our last one to close that will make it a full access control.”
It’s expected that the new overpass will be completed by the fall.
“The level of service will go way up. Mobility goes way up. In theory, it should reduce emissions, waste of gas and people sitting there waiting for a gap in traffic,” Burke said. “Safety, of course, is always increased overall. We’re way excited as a department to get this done.”
This article was originally published in the Rexburg Standard Journal. It is used here with permission.
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