There’s another article out about studying an interstate upgrade for the US 65/IA 5 Des Moines beltway.
There is more to an interstate designation than just signage. There are also rules about slow-moving vehicles and minimum speed limits.
Right now, the stretch of US 65 between US 69 and US 6 does not have a minimum speed limit. It did at the very beginning but was removed because once the old IA 46 bridge was taken out there was no way for farm traffic (tractors and combines) to get across the Des Moines River. (“Speed Limit Reduced on Beltway,” Des Moines Register Around Town East/North, April 22, 1998)
Here’s an excerpt from South Carolina’s driver’s manual (PDF, p.31, emphasis added):
Vehicles that cannot meet the minimum speed limit are not allowed on the highways. The only exceptions are farm machinery and construction equipment that is being moved a short distance and has no other way to get to its destination. This type of equipment is not allowed on the interstate under any circumstances.
There are very minor exceptions to the guidelines. The I-72 bridge across the Mississippi River, for example, allows bicycles.
Based on my understanding of the situation, the only way the entire beltway can get the red-and-blue shield is by reinstating a minimum limit, and that means restrictions on farm traffic (and bicycles).
The route could benefit greatly from a unified number, though, and I have suggested IA 435 (see bottom of page). That way, if the route ever did get upgraded, the number would already be there. An odd first number would not work because it is a bypass with both ends at interstates, regardless of whether the north end ever connects to I-35.