This is a bit off topic, we could create a new thread for this… but to answer your question: it’s the hardest part of a hike that determines the overall level of difficulty, so SAC 4 (alpine hiking)?
I think you have to ignore the names a bit, your example isn’t “alpine” hiking either but it does have a similar level of exposure as many alpine hiking paths:
But in terms of ‘hardness’ or ‘technique’ though it is SAC 2 - it’s terrain where we didn’t have to use our hands for balance. It’s just pretty exposed without any via Ferrata, which is a descriptor of SAC 4.
If you view it solely through exposure it would be at least SAC 4, if you view it as movement it definitely isn’t “Use of hands needed in order to advance in certain places” and would SAC 2. It has aspects of both ratings, but also mutually exclusive aspects. The descriptions on the wiki prioritize movement technique over exposure. Someone could argue is should be SAC T2 based on movement and be right, someone else could argue it should be SAC T4 based on exposure and be right. That’s non-ideal to me.
Something SAC T2 X would be clearer, but probably too granular for a wiki. 
You could also have SAC T4 PG where there’s a 2-3 meter tall bit of climbing to be done that isn’t exposed.
I don’t really think it makes sense to break this out, but something to think about with ratings.
A clearer way of putting it is I think the term is a bit ambiguous. I would personally find doing a 50km trail in one day demanding, even if it was flat and perfectly made just from a personal fitness standpoint. 
I’m not sure what I’d change it to, and it works pretty well.
A scramble is a scramble (it is referenced as a noun in T4 of the sac_state description).
I’ve also rolled my eyes a bit at the alpine climbing description as I’ve used it in the southwest. In this case we’re on a solid slab of rock that makes up a large ridge above treeline (mostly dwarf junipers) which is actually pretty close to the spirit of it. Here’s a shot looking down after we crossed over a pass and walked along the ridgeline a bit. The white/red layer on the opposite side matches where we were elevation wise, though in the previous photo we were above a higher side canyon.
I think dropping the mountaineering in my proposal above might be simpler. This is more thinking out loud than a formal language proposal.
highway=path - what any person able enough to walk and moderately fit is capable of doing.
Class 1 YDS, SAC T1-2, Austria Blue, SWW Yellow, CAI T & E
highway=demanding-path - might need hands for balance, or require some upper body strength (I guess a ladder or mantle would fall in here?) but you’re not climbing rock or have any significant direct exposure. having some experience hiking is highly recommended, but you don’t need to be a climber.
Class 2 YDS, SAC T3, UAII 1, Austria Red, SWW White-red-white, CAI EE
highway=scramble - requires use of hands to pull yourself up terrain. it’s generally simple climbing that is done without a rope but may be uncomfortable to people without technical experience and have fatal consequences. While far simpler than technical climbing, having climbing experience will help greatly. Via Ferrata routes with anything complicated than a ladder or a railing would probably fall into a scramble due to technique and physical strength required?
Class 3 YDS, SAC T4-6, UAII 2, Austria Black, SWW White-blue-white, BMC Grade 1, Schall Scale A, Hüssler Scale K1
(I’m not as familiar with Via Ferrata, I find myself usually skipping using it when in Canada, New Zealand, or Patagonia to just make my own way up rock and it isn’t as common in the US where I’m from.)
I think the best way to structure it would be to just map as many existing regional systems into overlapping categories so there’s something familiar for people to reference and then tweak. What are more European, Asian, or South American trail difficulty rating systems?
I think the best way to structure it would be to just map as many existing regional systems into overlapping categories so there’s something familiar for people to reference and then tweak. What are more European, Asian, or South American trail difficulty rating systems?
+1, in Italy there is the cai_scale
https://taginfo.openstreetmap.org/keys/cai_scale#overview
Hmm, there’s quite a jump from EE to EEA there. It’s like YDS 2 to 4 with no 3 in between, or SAC 3 to 5-6 with no 4. I edited my post above this with what it sounds like to me and the proposed mappings on the wiki page. I’m going to skip all the Via Ferrata, though I suppose that would automatically make it a scramble if it’s more than just going up a ladder.
On https://wiki.openstreetmap.org/wiki/DE:Key:sac_scale#Offizielle_Bewertungen_in_Österreich I put a table where I compare, from places that I visited, what OSM has on record in terms of as sac_scale and what on the ground is on the guideposts. I try a quick translate
You can see, there is much overlap. There is a chart below that gives a more theoretical view. In my mind, this is as much rubbish as the charts that compare YDS and UIAA. Some Germans seem quite fond of it, but in Tyrol, nobody uses the Swiss one. Our people are busy enough fixing the local system And yes, it is in flux!
One more word: Most of the OSM ways T5/6 do not have a guidepost. The „! Alpine ROUTE“ icon is a recent invention. It is used to replace black dots, where there is no path, merely a route. (This has to do with maintenance and liabilities arising thereof.)
When I was drafting the proposal, I read a lot about YDS. I learned, that it only starts at 5. Below, that is the Sierra Club scale. And there, a 4 is a serious climb.
I also learned, that the Brits (BMC) have a scramble scale. There 3 is a serious climb. So in the proposal, I only referred to YDS 2 rsp. Scramble class 1 as compatible with highway=scramble. Anything above would have to use a different base - highway=path comes to mind - I found it on UIAA VII climbing routes.
The CAI system is much too complicated for OSM use. Quite like the SAC Hiking scale (the original one) it is made to grade routes, not pieces thereof. And it makes that very clear, much more than SAC scale or Austrian grades.
For the sake of mapping things, I put red as just T3 @ RfC: Highway=Scramble - #82 by erutan - I don’t know any of these systems, or how they are used in the wild, so feel free to argue against my mappings and or point out new ones.
The Sierra Club is behind YDS, and the two are used interchangeably / the same thing. In fact there’s been like 4 historical versions of YDS which use the same ratings, though it’s been pretty stable since the 30s aside from Class 5 being continuously updated.
Class 4 can be serious, but it overlaps Class 5 up until about 5.5 or 5.6 - most climbing gyms don’t even bother with anything under 5.7 which generally has pretty easy holds and might not entirely vertical. YDS 4 could have some overlap T6. Class 4 is honestly a PITA as it’s the most ambiguous and only directly overlapping rating Class Four is a Myth: Problems in YDS : Articles : SummitPost
EEA referred to bolts, which seems to put it at YDS 5 / UIAA. T, E, and EE seems to fit well enough.
YDS 2 maps pretty clearly to SAC T3, which isn’t quite a “scramble” to me and would I think cover far too many paths. YDS 3 is clearly a scramble, and peak baggers would include YDS 4 as scrambling (honestly I’m not a fan of the new SPS scrambler rating as it makes the classic mistake of smushing together too many aspects of a path and calling Classes 2-4 all “scrambles” makes the word so broad as to be meaningless - that said having a 2.0, 2.1, and 2.2 gives me a little more information than just 2 even if at times I don’t agree with it). I think having a scramble and a demanding-path breaks up technique pretty nicely.
I’ll take a look at BMC.
update: T6 stopping at UAII 2 makes me think it does just top out at YDS 3, as UAII 3 seems to map to YDS 4 a bit better.
In Austria this would be a black path. Exposure is part of what is considered. There is no formal document by the alpine club, but the administration has some write-up regarding quality seals.
This has seen quite some shift, so hiking mostly is meant as only happening on constructed paths. See picture in the other thread.
I dropped CAI EEA as it seemed too technical and also dropped YDS 4, and I added in BMC Grade 1 to Scramble.
Scrambling skills: the grades explained BMC guide
I’m finding this useful https://www.bergfreunde.eu/alpine-grades-calculator/
Another example of why we need something like this:
The focus of my proposal was on the fun part. I like to ramble and to scramble - so I learned to say in the meanwhile.
The proposal went to vote, which turned out a belated RfC, so I postponed the vote. I am still willing to work on the details, e.g. spell out, why sac_scale just does not do it.
One prominent supporter was from the biking community - They like scramble, it is kind of a way to say this highway is not good for riding a bike
When I stopped the vote, a clear majority did support the tag, but not enough to pass the required 75%.
One more caveat: The Bosch appliance already brought about a nice encounter on me with someone on an unsuitable route, Bosch seem to be of the very careless kind of consumers. Short story: There may be routers, that interpret scramble as usable, just because it is in the highway key. Any knowledge on that?
Sooo… What’s the consensus on this? Should I be using highway=scramble? Looks like there are 22 uses so far.
I’ve tagged climbing access routes a few different ways and they all feel wrong to me:
sac_scale=demanding_mountain_hiking Way: 1163070762 | OpenStreetMapThese things do get notated on other maps, so they are useful to help people navigate (“Yes, you should expect to scramble here, it’s not class 5, you’re still on the right path”):
There is no consensus on this, a consensus would require 75% of approving votes in a proposal. (Nowadays.)
As the author of the proposal, I do, very little though. Still most of the 22 uses may be mine. I did not bother to check in detail. But in one case even a very influential person in OSM who opposed the proposal (because that might lead to erase hiking paths of national importance from OSM Carto, as far as I understood the argument) did not oppose me tagging a hw=scramble
Remember, tag-as-you-like.If it feels wrong to you, find something better - and BTW, please share your findings here!
PS: I do not see anything wrong in tagging climbing access routes hw=scramble if they meet the specifications I laid out in the proposal, i.e. must be at least UIAA I terrain - that is a term I am more familiar with. Not sure how to map a single 1m step (barrier=scramble comes to mind) on an otherwise walkable path though.
I believe that scrambles should disappear from normal maps. They are not something that people should wander into. They should not appear like a sidewalk or other constructed and otherwise flat path.
My understanding is that they are ways that require a certain skill and preparation. Scrambles should only show up on maps for people expecting to hike or something more difficult. Thinking sites like All Trails.
Sites like AllTrails do not show mentioned above hiking paths of national importance, because those are tagged T6 (ridiculously wrong at that, certainly no scrambles) - but OSM Carto shows them nevertheless.
All Trails also have a certain attitude on informal paths that IMHO is not actually helpful in way-finding.
The proposal was rejected, so I don’t think so. Or at least use it alongside highway=path, it’s doubtful that information would ever show up in a renderer.
Yeah that’s something I think about too. In the southwest US (Arizona/Utah) it’s not uncommon to come across a single mantle / very short T4 bit in what is otherwise a mostly T1-T2 trail with occasional T3 moments.
There’s a lot of stairs in the Sierra Nevada from the pack mule era like I described here. There were also some stairs in Canada in photos I outlined in the smoothness/surface thread.
One other twist is that an otherwise easily walkable trail can have a water bar which is more than 24cm high which makes it smoothness=impassible. Hazard seems most appropriate for something which very briefly increases the difficulty/technique.
Similarly, GaiaGPS by default hides any route with T5-T6 (you have to opt into a “mountaineering layer”). I think Caltopo stipples them differently and you can pull up metadata in a side drawer.
Whether or not they appear in normal maps is up to the map renderer @ IanH.
If anyone used it in areas that I create maps for, I’d definitely render it. I already have a “not turned on by default” layer for problematic paths (e.g. the higher sac_scale values).
I map lots of stuff that never shows in a renderer. The scramble experiment deliberately went at a crossing with highway=path fully recognizing the fact, that some so-called paths may vanish from renderers. The majority of the voters had no problem with this, but not enough for approval though. Reasons for rejection were a mixed bag. A noticeable amount due to people who prefer to have scrambles appear in ALL renderers and use sac_scale instead.
Using hw=* key also has problems, scrambles may not show on renderers, but some routers use them nevertheless.
