JEROME — On Thursday, folks got their first view of plans to reconstruct the South Jerome interchange — Exit 168 — on Interstate 84.
The current interchange, constructed in 1966, no longer meets standards, and the South Lincoln Avenue bridge over the interstate is structurally deficient, says Nathan Jerke, project manager with the Idaho Department of Transportation.
The proposed “divided diamond” interchange will be the first of its type in the state, Jerke said.
The innovative design will solve various traffic concerns, ITD spokeswoman Jessica Williams said, including greater separation between on- and off-ramps and frontage roads. The design will provide more roadway for increased vehicle volume and improve traffic flow.
Similar to a roundabout, all traffic from South Lincoln, Golf Course Road and both westbound and eastbound off-ramps will be directed counterclockwise — at 30 mph — in a nearly half-mile circle inside the existing frontage roads, Jerke said. The interchange itself will be just two acres larger than the existing interchange and take up considerably less area than a traditional clover-leaf design.
The project will also include longer on-ramps to allow more distance for vehicles to get up to speed before merging with interstate traffic, plus a dedicated bike path and a sidewalk for pedestrians.
The $20 million project will be funded with both federal and state money, Jerke said.
ITD hired J-U-B Engineers and The Langdon Group to work with local stakeholders to develop the new interchange design.
The interchange is designed to handle traffic through 2040, said Tim Blair, a project engineer with J-U-B. The two new overpasses will accommodate up to four lanes in each direction and will have a 50-year lifespan.
The existing overpass will stay in place during construction of the new interchange to keep traffic flowing as usual, Jerke said. The overpass will come down when the interchange is complete. Construction is expected to begin in 2020 and will take 18 months from start to finish.