There is only one good reason unsigned Interstates should remain--because the routes have been defined as part of the "Dwight D. Eisenhower National System of Interstate and Defense Highways," and such a definition beings federal funding equivalent to other Interstates.
However, since in every other system within the HB, the lack of signage prompts almost immediate removal, it's hard to justify keeping routes (even in usai) that are unsigned. Most (if not all) of these routes are not signed for the simple reason that they are concurrent with other well-established routes (e.g. I-595 in MD concurrent with US 50) and the Interstate signs were omitted so as not to overburden drivers with additional signs. When driving along US 50 in MD, it is easy to follow the signed route. If you didn't know part of it was also the unsigned I-595, you'd have no way of following field signage to clinch I-595 (even though you would be doing so by following that ~20 mile stretch of US 50).
For me it comes down to this. If you are going to argue that routes that are signed belong in the HB (such as usaush), you should not also argue that unsigned routes in other systems belong as well.
I'd lose some usai mileage if these routes were removed. That said, I'm strongly in favor of getting rid of them.
Keep in mind that this site is derived from Clinched Highway Mapping, which itself was previously Clinched
Interstate Mapping (and before that, the interstate highway browser). The interstates are in the site's blood. And the unsigned interstates are more prominent than other unsigned routes, especially as other unsigned routes tend to be there for inventory purposes only, whereas there is little benefit to doing so for an interstate (especially now that interstate-specific funds no longer exist).
If someone is looking to clinch routes, I would recommend going over TM to check out where things go. It's just a good idea, period, especially as many routes are poorly signed, and Google is often wrong.
Without them being mapped in TM, how would someone know how to properly clinch I-296, or anything in Puerto Rico (they aren't mapped in detail anywhere else on the internet, as far as I can tell)? I would think the status the interstate system has among roadgeeks as one of the holiest of holy things would be important.
I suppose if we must get rid of them, could we at least get a Puerto Rico Autopista system? That way PR wouldn't become a mono-culture of territorial routes, and maps with large numbers of routes and no color variation just don't look good. Actually, PR uses a variety of shield styles, so maybe there's an opportunity to split things (though they might not be
consistent - what the heck is going on there?).
I definitely do not think - "American roadgeeks might not want to learn some Spanish" (as mentioned upthread) is a good reason for getting rid of unsigned interstates.
How do you want to do this? A second .list user file for "routes I want to clinch?"
Maybe a way to list which systems that the user would not want to be shown... Hopefully not in a separate list file.
I always though some kind of declaration at the top of a .list file (ex: "EXCLUDE usaush") could be a way to remove systems one doesn't want from maps/stats, although I think there are people who would rather keep .list files for traveled route segments only.
