I don't dispute the traffic on US-412 around Siloam Springs, I was there 2 years ago (recommend Barnett's Dairyette) and yes, it gets bad. Upgrades, yes. Interstate? That is what I am struggling with.
Whether the corridor would carry an Interstate designation or not anything less than an Interstate quality super highway between I-44 in Tulsa and I-49 in Springdale is just silly. The NWA region may lack a single nationally recognizable giant-sized city, but the cluster of small cities all add up to something that feels like a giant metro anyway,
including LOTS of traffic. It's similar to the big cluster of Rio Grande Valley cities in the far South end of Texas, but with a higher average income level.
Pieces of this possible future Interstate corridor have already been falling into place. The first segment of the Springdale Bypass (AR-612) is open. So the connection to I-49 is done. Now they have to extend the freeway West to US-412. This Interstate corridor legislation might help spur progress.
A new bypass around Siloam Springs is the biggest, most difficult to build, missing link on this corridor. And a freeway bypass around Siloam Springs is 100% justified. I've driven the existing road a few times. The traffic gets pretty ridiculous. How to resolve the connection thru or around Dripping Springs to the Cherokee Turnpike is another hurdle, but not as bad is Siloam Springs.
US-412 West of the Cherokee Turnpike to I-44 is a 27 mile long stretch, but one that would be simple to upgrade to Interstate standards compared to a Siloam Springs bypass project. The upgrade would be as easy as the US-71/I-49 conversion project in Western Missouri. Just eliminate the at-grade intersections with a few more diamond exits or just bridges over the highway. Looking closely at the satellite view of US-412 in that area it's easy to see where ROW is already reserved for some future freeway exits (S4115 Rd, S4140 Rd, S4160 Rd, S4170 Rd, S4240 Rd).