I reached out earlier today on the sac_scale Talk page. Personally, I am afraid the MTB forum userbase might not be large enough to draw firm conclusions here.
I’ve come to think that, just like estimating suitability, labeling something as dangerous or impassable is highly subjective and probably shouldn’t be tagged explicitly. In contrast, passability is usually observable and verifiable—GPX traces, for example, provide solid evidence. Routers are already getting better at avoiding paths with missing data, so I see nowmtb:scale=passable/usable as a higher priority than tagging “dangerous/impassable” routes.
I agree that estimating suitability is subjective, so a mtb:scale=unknown tag should be considered temporary and should be replaced with a surveyed value as soon as possible. By tagging it as unknown, a mapper does not take an explicit position that a way is dangerous, but the value should imply that it is potentially dangerous and should be avoided by most map users.
Passability is verifiable so is easier to tag, but surely keeping map users out of danger is more important than offering them additional possibilities to enjoy their MTB ride.
Imagine that you’re an app provider that wants to provide MTB users with an idea of where they can go. In a small area of England, here is a list of where they can legally go (that’s not complete, but all of those are legally cycleable). In the same area, here is a list of ways with an mtb:scale tag. If you provide people with the latter list only, then there will be complaints, because in reality all of those legally cycleable ways could have an appropriate mtb:scale tag added, and many of those values would be at the easier end of the scale - they just haven’t been surveyed yet (in that area, by me).
Another possibility would be to give the user the choice, but here that’d be quite difficult to do without confusing users (think of the complaints that OsmAnd and Vespucci get for being “complicated”). It’s not unreasonable for an app to try and simplify things.
What we can do from the OSM side of things is to try and make it clearer when information is missing - in the different but related area of missing sidewalk tags, I created this (compare with the same area in a normal map here). I’m sure that that you can walk along the main road to the linear development to the west of the village there, it “just” needs someone to have a look at add the tags, and for that to happen it helps if something makes the omission obvious. It would absolutely be possible for someone to take the same approach for MTB tags; it “just” needs someone to do it (and overpass examples are a good no-code way to do that).
I can’t help but wondering if there’s an actual use case for this.
After all, if there’s no precise tagging like mtb:scale (and even if there is), the rider taking a path new to them will have to scout at a moderate pace anyway. And I guess the more adventurous among them already know too well how to take their bike on the shoulder.
On the other hand, an mtb-related tag may give a false impression of safety, or worse, be mis-interpreted as a green light by lazy map or app creators.
As a avid mountain biker I can’t think of a use case. What I need to know as a map user who likes to mountain bike is a trail “passable” for my skills and equipment. What this tag (whatever may be decided on) only tells us is that at least one person, with unknown skills and experience, riding with unknown equipment (there are a lot of different types of mountain bikes), rode (or walked their bike - we call this “hike-a-bike”) the trail on a bicycle.
I also wonder where the information will come from to populate this tag? If a mapper who is a mountain biker rode the trail then they should be able to apply a a specific mtb:scale tag. If a non mountain biker who is hiking the trail sees a mountain biker on the trail, they only will know that the specific location where they saw the biker was “passable.” The biker may have walked large sections of the rest of the trail. Also, these trails often exist as a web or network of trails, so at best, only the section between the intersections before and after the observed location could be judged as “passable” by someone walking the trail. Then we have the case of bike only trails. If you are on the trail, you are a mountain biker, and should be able to apply a specific mtb:scale tag. If you are not biking, you shouldn’t be on the trail.
I don’t mean to sound repetitive, but mappers around the world already use legal access tags for exactly this purpose — and as mentioned in this thread, several apps do as well. The goal here is to explore better solutions, without ignoring how tags are currently being used or why they matter.
Fair points. Think of it like highway=road — these aren’t always rendered, and they use a distinct style to give mappers a visual cue to survey them and refine their classification. Routers typically avoid routing through them. The goal here is similar: to provide an incentive for outdoor mappers (including new ones) to improve the map, particularly in poorly mapped areas with few contributors.
I think the main usefulness of a mtb:scale=passable or mtb:scale=impassable tag is of a temporary nature: it highlights a trail for survey by a mountain biker with possibly some OSM experience. Otherwise it only has a “better than nothing” value: it suggests that a trail may be easy or very difficult, but the end result should be a trail tagged with a proper mtb:scale=0-6 tag.
An mtb:scale=passable or mtb:scale=impassable tag should be mostly for armchair mapping and for use by mappers without mtb experience.
An armchair mapper may have read a blog about an mtb rider describing a trail as “fun” and with beautiful views, but without sufficient information about its difficulty. Or he may have noticed that a trail has a lot of heat for mountain bikers on Strava. This mapper could then tag the trail with mtb:scale=passable, in the hope that an mtb-experienced mapper will be tempted to go and try the trail himself and then tag it with a proper mtb:scale=0-6 tag.
I recently add this path Way: 1383928851 | OpenStreetMap because it showed as being used by mountain bikers on Strava and I didn’t know it yet. I added sac_scale=mountain_hiking and trail_visibility=good because as an experienced hiker, I feel capable to add them. It would be nice to add mtb:scale=passable too, to show that it is being used by mtb and as an invitation to survey it for mtb:scale=0-6 As suggested above, it could show up for Strava users as a request for review with 7 options with brief descriptions to choose from. I would also like to be able to add mtb:scale=impassable to this way Way: х. Амбарица - з. Ботев (844312515) | OpenStreetMap : it’s part of a long distance hiking route that is also popular with mountain bikers, but I think this part should be avoided by them (that it has sac_scale=demanding_alpine_hiking already gives a clue). While we were there we met a dirt biker who got stuck there because it’s impassable and too narrow to turn around…
Context: I live in an area where any path is by default legally ok to ride mtb on. Many already have mtb:scale, some don’t. None are ”dangerous”, or not more so than mtb riding inherently is.
One consequence of this is that that the condition of these unofficial paths changes a lot, as ”trail maintenance” is of questionable legality. Unpopular ones get overgrown, too popular ones turn into mudpits or ”root hell” as the ground erodes. Any mapping at all is of temporary nature.
I have a small objection to ”passable” as the value. Without the context of this discussion, it may lead to someone using that value for paths they managed to carry their bike through, instead of paths whose difficulty they don’t know. Mtb:scale should be about riding mtb, not hiking with a bike.
I record all my rides as ”road bike”, but I ride paths (it’s an allroad bike), and I may end up carrying it miles through forest for squadrats/wandrer purposes. Looking at my gpx, or Strava heatmap influenced by people like me, doesn’t give worthwhile data about rideability.
I think that for this type of mtb:scale value to have any worth, it needs not just a gpx but also a trustworthy account of someone (at least mostly) riding an mtb through it.
”Impassable” makes sense to me. If a path starts by 100 meters of hike-a-bike (or abandon bike and scramble forwards for silly gps games), I’m not going to micromap that path describing exactly how each part is unsuited for mtb riding.
Maybe mtb:scale=ridable would be a better value? We should describe the intention of the value on the wiki, but preferably choose a value that is as self-explanatory as possible.
A single GPS track on Strava should not be enough to map it as an mtb trail, but several of them could be, especially if also supported by an account.
mtb:scale=impassable would mean “impassable for the average mountainbiker”, while mtb:scale=6 means “impassable for everybody”
The wiki description of mtb:scale=6 is just completely alien to the kind of geography in my area/country, but theoretically, sure. A more realistic scenario for impassable is a deer trail through dense vegetation, or when heavy logging machinery makes a mess of the local water flow so a few years later you have paraller ditches that are overgrown with willow shrubs. (I’m aware of more accurate tags to describe this type of thing)
I agree with you — I don’t find Strava activity layers always reliable either. But a GPX from a trusted source would definitely be more useful.
Good point. But wouldn’t an impassable down/flat section that requires carrying the bike be tagged as mtb:scale=6? Carrying the bike does seem fairly common for steep uphill sections — e.g. mtb:scale:uphill=4 or 5. If that’s the case, maybe the examples in the wiki just need to be expanded.
Or maybe something like mtb:scale=traversable or another term would be a better fit?
Whether you are being repetitive or not, you are not addressing my point. My point about “no use case” has nothing to do with existing tags being misused. My point was that as a user of map data for the purpose of selecting a trail to mountain bike on, the information in the proposed tag had no value because I don’t care whether the trail as “passable” for some random rider of unknown skills with some unknown equipment, I need to know that is is “passable” for me.
If mappers are misusing a tag, we should attempt to gently educate them as to the proper us of the tag.
Can you give examples of apps that are misusing bicycle=yes?
How is a mapper, who is not a mountain biker, and who is unable to set a specific mtb:scale value supposed to determine what the “average mountain biker” is?
Allow routing through unverified trails? [Yes] [No]
I’m quite familiar with how OsmAnd handles rendering and routing—this would actually be quite simple to implement.
I understand your point, but it’s easier to assume a trail is feasible just based on tags like surface when there’s little incline.
Now, imagine living in an alpine or mountainous area like I do, where most trails are steep and potentially dangerous. In my region, the few trails that are tagged with mtb:scale tend to fall at the higher end of the scale (3–4–5), and most riders are experienced and well equipped. I think part of the issue is that mtb:scale was not meant as a general-purpose scale for cycling—it’s a scale specifically for mountain biking.
That said, I have no objection to using some kind of tagging approach to prevent routing over public but “unknown” or “dangerous” trails—at least until a proper mtb:scale value can be added.
What I struggle with, though, is this recurring idea I receive that information about trails being passable isn’t valuable enough to go into OSM. Yet at the same time, routers are allowed to send users down completely untagged trails with zero or little info.
As @tekim noted above (and others have noted before many times), “passability” isn’t a very informative value. One immediate follow-up question is: passable to whom and with what gear? Leather-soled oxfords? Hiking boots? Climbing gear? Normal bicycle? Mountain bike? At that point, the ‘passability’ value for all the different modes would just be duplicating other, already existing and more accurate tags.
I’d argue that routers shouldn’t send users down untagged trails. Or, rather, they should assume that way-elements with only a highway=path or =trail are in a very rough condition and route accordingly.
We cannot prohibit data users, including routers, from doing anything (other than license violations).
However I personally would strongly suggest that routers should not send users down completely untagged trails. Doubly so in mountainous areas (routers have separate elevation data, right? so they know where mountains are).
In this specific example this could mean not creating MTB routes in mountainous areas through ways that don’t have mtb:scale tagged. Or if there’s concern about a short untagged way breaking a whole route, at least giving a very very large score penalty and returning a warning.
I care. If someone can ride it, it means the path is at least wide enough to fit mtb handlebars. So (in my area) worst case scenario now is that I have to carry my bike through some sections. Without tags, worst case is I can’t get through at all without a machete.
Perhaps. But notice that we’d have to have similar tags for at leastbicycle:scale=*, foot:scale=* and hiking:scale=*. We need all the different modes to be present as none of these passable values for the different modes are immediately and truth-preservingly inferable from each other.
Indeed, your point about handlebar length is spot on! A path that is too narrow (wrt. the handlebars) for a normal bicycle might be ‘passable’ for a mountain bike, and a path too narrow for a mountain bike (wrt. the handlebars) might be perfectly fine for strolling with leather-soled Oxfords. And this was just about the width of the path. Similar considerations apply for e.g. incline, etc., etc., etc. Like I said, at this point, were simply duplicating a few descriptive tags with a needlessly contrived, somewhat subjective (as @tekim noted) and mode-specific tagging system.
I respect that you may not find it useful, but passability matters to others. Many mappers, in my region and beyond, (mis)use access tags to indicate passability or impracticality, which shows it has real value. For example, in Israel—even as mentioned earlier—some map providers interpret bicycle=yes on highway=path as “passable with unknown difficulty.” You can also find plenty of related usage on sac_scale with values like ?, fixme, yes, and unknown here.
If you’re worried about adding new values to mtb:scale, that’s understandable. But at minimum, supporting mtb:passable=yes or suggesting another option would help. Dismissing current usage and its importance only contributes to tag misuse.
That is precisely the goal: to create a generic solution, whether through a new scale value or an additional prefix/suffix tag, as emphasized in the poll.
