Have you taken a look on your wikipedia link? There are some pictures of ways. None of them is “uncomfortable to walk on”. I would rather say, when a wheel can roll on a way, it’s somehow comfortable to walk, since the surface is rather smooth and usually kind of solid.
Are you talking about Tag:sport=mtb - OpenStreetMap Wiki ?
If that’s so, I would keep singletrack out of your proposal and include “natural” single tracks in the trails part of your proposal.
Yes, I did and I also saw some single-tracks in the wild and walked on them. Did you? Have you ever seen a single-track? The wiki says:
Many mountain bike riders prefer singletrack over other types of trails, as singletrack is usually designed specifically for the sport, and therefore can have elements which highlight features of the sport (whereas other trail types will usually be more straight, and not exhibit as many hills and other special features).
That is my experience too. You can see it even in the picture in the wiki:
A pedestrian wouldmost comfortably walked along hte red line. For a biker going downill, momentum makes the yellow line more logical and enjoyable (though note this is not a great example, the difference is faint). “Comfortable” was not the greatest word, better would have been that they are not straighforward to walk on or something.
Not necessarily. This tag could be used alongside a single_track or not. I maintain they are a special kind of a way deserving their own tag. or example downhill slopes could also be tagged with Tag:sport=mtb - OpenStreetMap Wiki.
I’d describe mountain bike single track as awkward, annoying, or sub-optimal for walking. Here’s an example of a mountain bike single track section:
This flowing s-curve with banked turns is very clearly designed with fun on a mountain bike in mind, not ease of walking. One could certainly walk on this but the angled trail surface and unnecessarily exaggerated curves would feel awkward. If the trail were designed for walking it would be more direct and the curves would not be banked/angled.
That being said, shared use single track trails that aren’t so mountain bike specific also exist.
Single track is just a synonym for a trail that is not double track. In other words, a path that is not wide enough for a 2 track vehicle. It’s use may have been popularized by mtbers, but the term doesn’t mean it is was designed by, or for, mtb’s.
In other words, singletrack is highway=path, and doubletrack is highway=track? 
Sorry for being out of the loop on this thread the past several days. I was at a cartography conference. The organizers must have been thinking of all of you, because they chose to hold the conference at a hotel with this inviting-looking not-a-crossing directly in front. foot=no wheelchair=yes, I guess. 
But what is the inverse? Wheelchairs are legally allowed almost anywhere pedestrians are, but the law expects wheelchair users to know their limits. I have pretty much only ever seen wheelchair prohibition signs on escalators and the occasional steep incline, just in case. A narrow doorway never comes with a sign warning wheelchair users not to take out the doorpost when ramming through. Does that mean wheelchair=no should be nearly nonexistent in OSM?
The access restriction documentation recognizes that wheelchair and stroller users need information about physical suitability much more than they need to know where they’re legally allowed. Why only them? Why not also recognize that the legal right to scale a fence on foot, or freestyle down a flight of steps on a bike, would be out of scope for a mapping project?
I don’t think anyone is actually arguing for such extremes. So when we say that some mappers indicate suitability using access keys, let’s give them the benefit of the doubt too.
There’s a certain elegance to this approach, but it requires us to depart from the notion of highway=* as a thematic key, limiting it to things actually called highways.
By the way, the more poetic option would be byway=*, as in the phrase “highways and byways”. Others may know better, but I get the impression that a stereotypical British byway would be an obvious highway=path today, or at most a highway=track.
That said, moving paths from highway=* to byway=* would potentially cause two kinds of confusion. One is the British legal designation byway open to all traffic (BOAT). As I understand it, a BOAT could theoretically be any kind of road, track, or path, even a nonexistent way. BOATs are tagged designation=byway_open_to_all_traffic; we might have to educate mappers about the difference between a way’s identity and its legal designation for the purpose of limiting access.
The other issue is that North American English seems to have all but forgotten the term byway, except in the names of heritage road routes, such as the Ohio River Scenic Byway, which goes over nothing but well-paved roads and even some stretches of freeway. Fortunately, speakers of these dialects are used to words like “trail” and “byway” clinging to more car-centric infrastructure.
Anyhow, even a more elegant byway=* key wouldn’t solve any of the logistical obstacles that have been raised around pathway=*. I bring it up only as a curiosity, for completeness’ sake.
Well, Cambridge dictionnary gives this definition.
I think highway= is overloaded but after discussion I am not sure it is feasible to move a chunk of it elsewhere…
As a rule of thumb, a one-line dictionary definition isn’t going to carry nearly as much nuance as an encyclopedia article. But you have a point that the word can be flexible.
A well-constructed back road would very well meet the definition of a byway to an American, who would consider a “small road” to have fewer than four lanes. The only qualification for a byway here is that it evokes nostalgia for a bygone era. But all you have to do is peruse a gallery of English byways to get the sense that byways there are mainly about something much more primitive. From a legal standpoint, the following photo is apparently of a byway open to all traffic, probably because it’s built well enough that it can be used by vehicles as an exception, but still conceptually closer to a cycleway, footway, or bridleway:
Even so, it seems like a byway can also be thought of as a subclass of highway, bringing us right back to the starting point.
Agreed. Maybe this triangulation would at least help us come up with more intuitive presets or documentation.
In England and Wales, we already have to do this. 
All of the English/Welsh legal PRoW types use words that have a more common meaning in the language (e.g. footpath). On byway, just to throw in another example in, the National Byway is the name of a cycle route that meanders around the country mostly on minor roads. Here’s one section in OSM.
Obviously that’s the driveway for horses to be “parked” in front of the hotel/saloon. After the hotel was sued by several cowboys after their horses hurt themselves at the kerb, they lowered it. 
In my understanding, highway=* are mainly ways you use to get from A to B and leisure=track + sports=* are ways you use for “fun”. Like the 400m race loop in the stadium, or raceways, or most of the climbing routes. In a similar matter I would treat those mtb-trails. If the main purpose is having fun on the downhill ride, than it’s for me not a highway.
I hiked as well also hiking trails with such inclined curves due to water drainage after rain. As usually the inner curve is where the water removes material and it builds up on the outer curve. For me such inclines are not really “hard to walk”, I don’t need to pay any special attention where I put my feet and in my opinion that’s nothing we should classify a trail about.
Besides this, a trail where you need to step from rock to rock is as well “not easy to walk” or Roman cobblestone “roads”… Just to keep in mind for the wording.
I just did upvote your comment I am consistently amused that even seasoned openstreetmap contributors (ab-)using brouter get caught being tricked into following via ferratas as if they are anything but a fun endeavour, just because via_ferrratas live under the highway key, which is supposed to map ways to get ordinary persons from A to B. While it my seem too late to change that, after all, I’d say, brouter right on this!
Raceways are actually highway=raceway and usually go right back to point A at the end. The wiki could better clarify how to use these highways, like the coach in this interview:
In case the proposal passes (I will abstain without notice) – in the aftermaths: Clean all references toT1…6 – those are prominently used on hikr.org referring probably to the 2023 specification issued by the SAC yet starting a dozen years or so ago in this vein. You might also remove any reference to colours, as those are not part of SAC scale but of “Schweizer Wanderwege” (a QANGO) that maintains most of hiking paths in Switzerland (the SAC NGO most only maintains the access paths to its huts, a very minor part.)
PS: Swiss community urged to correct any mistakes in my outside view.
Where I’m mapping, yeah, pretty much: double-track = 4 wheels, single-track = 2 wheels.
But honestly, I’d avoid using “singletrack” for any new tags—it’s got way too many meanings. Just check out the Wikipedia page on single-track roads!
It’s a bit like “alley”—a single word that has stirred up a whole lot of confusion and conflicts in the OSM community.
I would be very open to having all paths/roads that are more or less for sports only (via ferrata, scramble, climbing, downhill singletrack, even race tracks for cars, horses, or bicycles) under a common tag like leisure=track. But the difference between a raceway and a climbing path couldn’t be bigger, so it would feel a bit wrong to only use sub-tags to set them apart.
leisure=track+sports=*are ways you use for “fun”. Like the 400m race loop in the stadium, or raceways, or most of the climbing routes.
for climbing routes? is there a „track“?
Following your reasoning, when there is a hotel which is only chosen by tourists because it has a great view, one could decide to map it as tourism=viewpoint with hotel=yes or viewpoint=hotel?
IMHO a track made for pleasure, but integrated in the highway network (unlike a bike circuit which is on a dedicated ground and running in circles without the possibility to use it to get somewhere else), should be tagged with highway (as well, at least).
or Roman cobblestone “roads”… Just to keep in mind for the wording.
to nitpick about wording, roman roads are stone paved but the stones are not cobblestones 
As much as there is a highway on stairs or your ladder. You have to see the big picture. Would you prefer sport_highway=climbing 
?
Whatever it is, it probably belongs to leisure namespace rather than highway. For example, there is somewhat documented leisure=climbing tag which may or may not be the optimal solution.
