Unless you meant "MTB", in which case they don't seem to make it quite so easy to know. Ask the district office?

You already have your answer since the MVUM literally the legal document that allows motor vehicle use. If it's not there, it's not legal. This one has a locked gate to enforce the closure, but there's enough room for a little parking.

These were switchback cuts of the sort that result in no tread at the upper section and either a pile of dirt or no trail at the bottom. Sometimes the fact that people will ruin million dollar trail so that they can cut 10 feet off their journey while out for exercise really bugs me. Others were squiggly little lines diverging from the main trail by a few feet and for not very far. Most would take these as part of the already marked but overused trail. There were plenty small diversions like them not marked. One was along the main trail and after moving the trail, I'm not transferring over the little nonsense.

Everything that constitutes a unique route is still there.

I have never seen TR as part of a ref in an official way and it doesn't add any information. These types of prefixes are used to distinguish roads from different agencies. There's nothing to distinguish here and "TR" wouldn't do it anyway.

Oh, the IAT is a thing. There's a Wikipedia entry and everything. There's IAT stuff in Greenland, Iceland, and Europe too. Fellow I know who sort of did it started with the Florida Trail (Eastern Continental Trail) and had to skip Quebec for hunting season. Instead, did pieces in Newfoundland, I think. I might have a go at getting some of the California Coastal Trail in a relation. With the Oregon Coast Trail, it's a larger Coast Trail. I'm not sure if Washington and BC have gotten in on the action. Very incomplete.

Incidentally, one of your "alt-cdt" (going north from Dillon) was showing on my map at far zoom when it was rendering anything in a relation, but not at close zoom. I found it had been tagged "route=path" instead of "highway=path", which my software didn't know what to do with. (I use files from OpenAndroMaps rendered by c:geo or OruxMaps to have offline maps.) It also was really rough, so wouldn't have been any use at close zoom anyway.

I can assure you, the forest has not been working on that trail. In 3 days, I met only two people who were in the span of half an hour on this trail. One was a section hiker who didn't think the standard CDT was in his capabilities and the other was setting up for hunting season. I saw more moose.

Fixed a "fixme" on a trail created near Silverton the Forest Service topo calls Ptarmigan Loop. This trail was generally visible in photographs especially with hints from Strava heat map. I'll continue working on this route over Ptarmigan Pass and along South Fork to Bobtail (which is stuff I hiked, unlike this one). Just wanting to let you know that better trails may be possible now.

I'm having trouble figuring out exactly which edit this is referring to. I was sent a map with my backpacking permit that shows Redwood Creek Trail to extend between Tall Trees Grove and Emerald Ridge. I walked it and found it to be somewhat different from what is shown on that map, but the gist is the same since it is frequent fords between gravel bars and some trail beside trees. The exact fords and gravel bars will change yearly anyway.

USGS in this area is extremely old. This part of the trail is covered by two quads, one of which doesn't even know there's a National Park there. So, no, you don't see the trails the park has built on there either. I used personal research. My GPS track is public, but it includes excursions into the trees, so I also used my then recent memory of hiking the thing.

I did find the large number of logging roads that have been transferred from the 1960 era USGS map to be misleading when I hiked the horse trails on the west side of the creek. Some of them have been actively removed and others vanished quite cleanly on their own.