The first DDI in Ohio was built on I-270 outside of Columbus, Stanley said. Another has been installed at I-475 and Ohio 25 near Toledo, according to ODOT’s website.
The DDI uses a “continuous flow” design with fewer traffic signals and left turns, Miamisburg City Manager Keith Johnson said.
Pedestrian and bikeway upgrades along the interchange area, meanwhile, have long been discussed by Miamisburg and Miami Twp., but funding has remained a question.
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The two projects combined, estimated to total $6.8 million, would cost the city about $300,000 and the township itself nothing — if a federal grant can be secured, officials said.
“When we did the math,” Johnson said, “we just said ‘get this done.’ ”
The DDI concept has far fewer “conflict points” than the current pattern for the Ohio 725 interchange, which should make the number of accidents “plummet,” Johnson said.
The DDI design would redirect traffic using “free-flowing turns when entering and exiting an interstate,” according a transportation video.
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Separated by concrete barriers, “both sides drive on the opposite side of the road before crossing back and resuming their original pattern,” the video states.
The DDI design is similar to the Austin Center interchange at I-75 that the city and the township also share with Springboro, but it has fewer traffic signals, Stanley said
Meanwhile, coupling the DDI plan with proposed pedestrian and bikeway improvements would require hitting a Wednesday deadline for a federal environmental grant that could finance 80 percent of the upgrades, according to the TID, which plans to allocate $250,000 to the project.
If successful with landing the federal grant, the local share for all $6.8 million in upgrades to the interchange would be $429,000 – about 7 percent of the total cost for both projects.
Stanley said he is optimistic that the package “will be 100 percent successful. It’ll be a while” he noted of the 2023 start date. “But we will be pushing to do it faster if we can.”
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The plan to seek the federal grant has been approved by Miamisburg City Council and the Miami Crossing Joint Economic Development District board, a tax-sharing entity formed by the city and Miami Twp.
The pedestrian and bikeway improvements “begin and end” in the city, running roughly from Byers Road to just west of Ohio 741, Johnson said.
Miamisburg would fund 70 percent of the work while the Miami Crossing JEDD would pay for the remainder, officials said.
The $300,000 total for Miamisburg is equal to about three years’ worth of minimum disbursements the city receives from tax collections from the Miami Crossing JEDD.
However, should federal funding be secured for the pedestrian and bikeway proposal, that project would likely be financed through a State Infrastructure Bank loan, Stanley said.
The SIB provides low-interest loans and – under its guidelines – no payments would be required until 2026, he added.
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COST SHARE FOR OHIO 725 PROJECTS
•Total: $6.8 million;
•ODOT: $4.09 million;
•Federal grant: $2.1 million;
•Montgomery County TID: $250,000;
•Miami Crossing JEDD: $128,700.
SOURCE: Montgomery County Transportation Improvement District.