JEROME, Idaho — Apparently a normal interstate interchange was not dramatic enough for Idaho.
While the rest of the country was busy building ordinary ramps, overpasses and intersections, Idaho took one look at Interstate 84 near Jerome and basically said:
“Hold my Red Bull.”
The result is the new South Jerome Interchange, a massive looping highway configuration so enormous from the air that TWOSU News is officially dubbing it:
The largest roundabout in the world.
There is just one small technical problem.
It is not actually a roundabout.
The Idaho Transportation Department calls it a Divided Diamond/Couplet interchange, which sounds considerably less fun and slightly more like something invented during an engineering meeting that ran three hours too long.
Construction began in 2024 as ITD moved to replace the aging South Jerome Interchange, and the project is scheduled to wrap up in November.
From the air, though, none of that matters.
It looks like somebody drew a giant racetrack around Interstate 84 and then asked the construction crew to make it real.
New ramp opening Wednesday
The latest phase of the project arrives Wednesday morning when ITD expects to open the new eastbound I-84 off-ramp by approximately 6 a.m.
Before that happens, drivers will see several temporary changes.
Southbound Lincoln Avenue traffic will shift onto the northbound bridge over the weekend.
The eastbound I-84 off-ramp will then close from 7 p.m. Tuesday until 6 a.m. Wednesday, with motorists detoured to the Main Street/State Highway 25 interchange at Exit 165.
Southbound Lincoln Avenue traffic is expected to move back to the southbound bridge by Wednesday morning.
So yes, for a brief period, drivers will be moving across different bridges, taking alternate exits and following construction signs through something that already looks like an interstate-sized Hot Wheels track.
Truckers, this thing was designed with you in mind
For commercial drivers, there is actually some real engineering behind the madness.
ITD says the interchange is intended to improve safety, increase traffic flow and provide better connectivity through the growing South Jerome area.
The project also accounts for truck traffic.
The agency has previously said trucks need additional acceleration distance when entering I-84, so the new design includes longer ramps intended to give commercial vehicles more room to get up to speed before merging.
That is especially important in South-Central Idaho, where I-84 carries a significant amount of agricultural, food-processing and freight traffic.
So while the interchange looks ridiculous from 500 feet in the air, there is a method behind the madness.
Mostly.
Idaho apparently rejected boring
ITD evaluated numerous alternatives before settling on the unusual couplet configuration.
The design separates frontage-road traffic from interstate ramp traffic, adds controlled intersections, improves pedestrian connectivity and is intended to handle future growth.
In other words, engineers had a legitimate transportation problem to solve.
They just solved it with something that looks like a NASCAR oval swallowed an interstate.
The original interchange dated back to 1966, which means Jerome went from Eisenhower-era highway design to something that looks like it belongs in a video game.
Important clarification: do NOT drive it like a roundabout
Despite what your eyeballs may tell you, motorists should not approach this thing like a traditional traffic circle.
There is no giant circular lane where everyone keeps driving around until they panic and take the wrong exit.
The design uses separate roadways, bridges, ramps and controlled intersections to move traffic around and across I-84.
So please do not enter Jerome, see the giant oval and decide you are suddenly in Paris.
The Idaho way
Other states build conventional interchanges.
Idaho builds something visible from low Earth orbit.
And honestly, after looking at the aerial photo, there is really only one appropriate summary:
Engineering textbook: “We recommend a divided diamond/couplet interchange.”
Idaho: “Can we make it look like the biggest roundabout anybody has ever seen?”
Engineer: “Technically it wouldn’t be a roundabout.”
Idaho: “Did I ask?”
Engineer: “No.”
Idaho: “Hold my Red Bull.”
The South Jerome Interchange is expected to be completed in November.
Until then, slow down, watch the construction signs and remember:
If you find yourself completing three laps around Jerome, you have misunderstood the design.
