There are grab-bag systems and then there are well-signed national tourist routes. IMO, a system including Historic 66, the Lincoln Highway, Great River Road, the signed Circle Tours, other national scenic byways would be analogous to eurtr, nzltr, and sctntr. Most of these are very well signed and all fall under "tourist routes".
I'm glad you said well-signed national tourist
routes, and not systems.
For usaush, the "well-signed" part may apply to some routes and some jurisdictions, or certainly doesn't extend to the system as a whole.
Do we really need criteria?
It certainly beats an "any old rubbish" approach...
And my point is that this applies to pretty much every system in North America. "Updates to Highway Data" has about as many threads on routes being unsigned and thus must be removed/routes now being signed and thus now can be included, as it does on construction occurring.
What sets usaush apart from the formal state systems is that we have
only signage to go on. With the regular state systems, when signage is incomplete/inadequate, we at least have the "on paper" definitions to fall back on, to shed some light on where the route goes, what's "supposed to be" signed. With historic routes, we have no such luxury. When there's next to no signage, or just one lone sign in a random downtown, we don't have much of a definition of a route.
