My point is that we as contributors must rely on field signage to know what a route is, and what there is to include.
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.
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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".
Very open to this, but oscar's point about selection being an issue is a very valid one.
I will point out that 'National Scenic Byways' (in capitals) is rather a messy system, even just the more elite 'All American Roads' - with a lot of branches and bifurcating loops and stuff. There's perhaps a few routes that are coherent, signed reasonably well, and not fully part of other systems (a lot of routes are entirely concurrent with just one route) AARs/NSBs that might be worth considering. The 'Historic Columbia River Highway' AAR would be one to add (as US30His?) to a more grabbag system. Las Vegas Strip AAR, perhaps could be, despite its short length (in part because it is very well travelled) - though I don't think it's signed. On the other hand, there's at least
a site with maps and legal definitions - the lack of which is one of the things that annoys people with usaush.
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Some of the disjointed sections of US66His in Missouri are hard to follow. When I drove it in late 2018, there was no signage on US66HisLaq other than "P" and "AA" though there was signage for Historic US66 on MO17 in the same area. If US66HisLaq had not been in the HB, I would have never known it was an old alignment of Route 66. If being signed it the determining factor, this 2.52 mile segment needs to be removed.
Fair enough. Certainly, however, it wouldn't have been included if there wasn't at least one sign at one point - as the system has gone through several purges of unsigned routes.
I stick by my original thought. usaush is NOT a system. It is a list of old alignments of routes that have been moved or decommissioned.
Arguably it's no more a system than a collection of routes that all share similar shield signs. However it's not a list of old alignments of routes that have been moved or decommissioned - it's far more selective than that, relying (like most other systems) on signage, and there's many (thanks US20His! though also US6His too) bits where the historic route is sharing pavement with the current route.