OTOH, Wisconsin has a ton of Alternate Interstate routes. They are well-signed enough to be used as emergency detours to bypass Interstate closures. None of them are in the HB, except where an alternate route happens to overlap with a regular state-maintained route. I think there is no interest in adding them, or similar routes in other states, to the HB.
For a counter-example in Saskatchewan, when the highways ministry built a route 39 bypass of Estevan, it moved 39 to the new road, but kept the old road through downtown and renumbered it 39A. That's not what it did in Regina, or Moose Jaw.