"See _____" or "Discover _____" signs in Oklahoma

[Road Hog]

Well, a lot of it has to do with how I-35 was planned/constructed in Oklahoma. In most cases the Interstate was built as a direct upgrade of the old highway, with bypasses around the towns. This leads to a natural setup for a business Interstate route, since you have one road, the old highway, that goes straight through town while the main road curves around it. The I-40 business loops in western OK are a great example of this model, as are some of the I-44 loops in Missouri.

That's not what was done with I-35. Instead, I-35 was built as a straight line one mile to the west of US 77. As a result the whole thing is one big bypass. There is not a set up where the old highway "reunites" with the new on either side of town.* Instead, in most of the towns you might consider to be of the right size to have a business loop, like Pauls Valley or Wynnewood, there is usually a typical cross intersection of US 77 and a state highway, and you access the town by using that state highway. In any event there is usually little reason to do so since most of the businesses set up shop by the Interstate, not downtown.

*Purcell has a setup that would work well with a BUS I-35, but much of it was not all US 77. SH-74 comprises much of the loop, concurrent with US-77 and SH-39 on the south side of town. The far north bit of the loop is not under state maintenance but was once SH-74G. Arguably this whole loop should be BUS I-35, if you feel BUS routes materially help a city out, but if you don't it will probably seem senseless to add yet another highway to the mix.

This is the typical eastern model, where interstates were built as entities completely separate from the legacy U.S. routes, and the U.S. routes maintained their original designations as if the interstate were never built. In the west, interstates were built on top of the original routes and then as bypasses around towns; thus, there was little justification (beyond nostalgic) for maintaining the U.S. route designations. Especially after California cut off the ends of the original routes, inducing its neighboring states to decommission their old U.S. route designations as well. To maintain the Central States major topic category, I would use Minnesota as an example of a state that chose to eliminate or duplex with the interstates its legacy U.S. routes where they were bypassed by interstates. Nearly all of the original U.S. routings along the alignments of interstates in Minnesota now exist as county routes; still in existence and drivable, but marked and funded as local roads, as the state did not want to maintain two trunk highways in such close proximity. It'd be interesting (as I don't have these data) to compare traffic volumes and destinations (local vs. longer distance) of marked U.S. routes that exist closely parallel to interstates, as in the east and southeast, compared to states that follow the Minnesota model.

Arkansas kept the dual U.S.-interstate pairings intact with I-40 (U.S. 64-70), I-30 (U.S. 67) and I-55 (U.S. 61) for the most part, although there are some duplexes in the vicinity of Little Rock. In each those cases, along with U.S. 65 where I-40 dips south between Conway and Little Rock, the old U.S. alignments remain as state highways.

On the other hand, Texas has been more liberal in either duplexing or doing away with U.S. routes. U.S. 67 parallels I-30 south of New Boston but is subsumed by it somewhere between Mount Vernon and Sulphur Springs. It re-emerges in South Dallas. U.S. 77 disappears at the Red River, reappears briefly through downtown Denton, disappears again and re-emerges in Waco. The old U.S. 75 south from Dallas is now SH 75 along I-45 basically from Richland to Conroe.

[agentsteel53]

former US-10 is an example of the interstate being built next to, as opposed to on top of, the old road.  as a rough eyeballing, I'd say about 60-70% of US-10 is drivable between Fargo and Seattle.