RFC: hiking_exposure key (along with hiking_technique this disambiguates sac_scale)


One issue with sac_scale is that it covers both difficulty and exposure (and makes some other assumptions that can be disregarded). If a trail is T1 in technique, but T3 in exposure, it should be tagged as T3. However anyone looking at that tag has no idea if it’s partially or completely T3 terrain.

They might be fine with being on a trail that is near the edge of a cliff but dirt single track, but not on a T3 technique with T3 exposure trail.

As a real world use case my partner and I, in standard hiking/backpacking shoes/boots are more comfortable with exposure the less technique there is. It’s uncommon, but not that much of an edge case for a T2 technique path to have a T4 level of exposure. T2 exposure and T4 technique is fun, T4 exposure and T2 terrain is perfectly fine as long as it’s reasonably trustworthy, but they are different from T4 terrain and T4 exposure (which I’d have to tag it as with the existing system).

As my partner put it:

Yeah it’s where disambiguating exposure and technical difficulty is the difference between “if you don’t like heights you’ll hate this but a 5 year old can do it” and “there’s a chance you could die if you don’t know what you’re doing"

I basically had this written up for another project, so I’d propose borrowing the US Yosemite Decimal System movie star rating for protection while climbing and applying it to exposure as it’s probably easier for the average person to understand. At least were a similar movie rating system exists, but I assume Hollywood movies make it to most places.

Note: this pairs well with hiking_technique. :slight_smile:

Class 5 has “movie rating” risk modifiers regarding the distance between aid placement - for unroped travel in simpler terrain they will refer to the general risk associated with a fall due to exposure. It’s worth noting that you can sprain your ankle stumbling in a parking lot or crack your head open tripping on a sidewalk, so you’re never risk free. :slight_smile:

This is basically:

  1. not exposed and no real risk of falling
  2. feels scary but no real risk of falling (skywalk trail, via ferrata protection, etc)
  3. greater risk of falling, but still unexposed
  4. indirectly exposed, falls could be serious but somewhat unlikely
  5. fatal exposure, you lose traction you dead

Key Values

0 - Unknown

Topo and knowledge of the general area can help guide you. Paved or gravel trails are unlikely to have significant risk. Default value.

1- No Fall Danger


A fall would just be onto a path. It might be painful, but should not result in a major injury. What would be considered “G” terrain would generally be applicable to proposed hiking_technique=casual_walking terrain, though you can have nice smooth single track trails that have direct exposure on the side.

Someone could trip and sprain their ankle or “bruise their nose”, but no significant risk.


2 - Airy but Safe


This would include areas that “feel” very exposed and airy, but are constructed in a way to keep people safe. The SkyWalk in the Grand Canyon is a great example - it’s casual_walking terrain with no real risk, but you have to be comfortable walking out over a thousand drop with glass under your feet. Via Ferrata routes where there are guide rails to prevent falls or cables to clip (Half Dome in the US, many peaks in Europe) into would also fall into this category.

People very sensitive to exposure may be unable to proceed, but there is little to no actual elevated risk.


3 - Short Falls Possible


There’s no big drops or significant risk of serious injury or death, but you could easily get banged up if you fall a short distance or lose your balance. Uneven and/or loose terrain makes this more likely than on safe terrain. hiking_technique=use_of_hands terrain is always at least at this level, as you could lose traction and slide down a steep slope and sprain a wrist or ankle, land awkwardly on talus you’re moving across and snap a bone, or have something similar happen.

People very sensitive to exposure may be uncomfortable, but it is within the average person’s comfort zone. Some amount of elevated risk is present but consequences should be minor to moderate.

SAC T2-3?

4 - Exposed


While it’d be possible to walk away from an accident on this terrain it could easily result in moderate to serious injuries. This includes:

  • A 15-20 foot drop within a foot or two of you. This will commonly be traversing narrow ledges or climbing small stretches of cliff face.
  • A larger drop a couple of feet away that should be easily avoidable. This is a bit tricky as a fall would likely be fatal, but the exposure is indirect enough that it doesn’t pose an imminent risk.
  • A steep long slope that isn’t conducive to being able to easily stop a slide resulting from a fall (smooth slab etc). Would be fatally exposed (X) if there is a sheer drop below it.

People not overly sensitive to exposure may feel uncomfortable or unwilling to continue. While risk is not so elevated as to be “one mistake and you die” significant risk still exists.

hiking_technique=scrambling is generally at least exposed, and can be fatally_exposed.


5 - Fatally Exposed


Sections with enough of an immediate drop that either a mistake in movement or a failure in terrain would most likely result in death or injury requiring evacuation. Even a 30 foot fall onto a hard surface is often fatal unless you can land in a controlled manner. Direct 50-80 foot falls are generally fatal without extenuating circumstances.

People not comfortable with exposure can easily end up dead.

SAC T5-6?

I like the attention to detail here, even if I don’t completely follow it. (It is tedious, and seems to have great merit, but I am not an expert and don’t feel qualified to judge it very well).

However, I’d like to remind that the “movie rating” values choses are from the MPAA (a USA-based system) and that these values (and boundaries) are different in other regions across the world. [G, PG, R, X], as “General Audiences,” “Parental Guidance (suggested),” “Restricted,” and “X” might speak for itself, but is dated (X has become NC-17) will be seen by 95% of the human population as “huh?” while the 4% or 5% of our human population in “American” (USA) culture will recognize it.


I don’t know anything about hiking, and haven’t kept up with discussion. But as you aren’t using any standards, you should use full readable words for both, not alphabet abbreviations.


This was originally written for essentially a fork of YDS to be applied to Class 1-4 terrain, so the movie scale rating makes sense in that regard and actually maps pretty well psychologically. I feel like I’ve seen these ratings on US movies when traveling abroad so figured they might be more universally known.

general audiences
guidance suggested
adults only

I already had “human readable” words next to the ratings, so having to paraphrase for G (I originally dropped it as the system is geared around off-trail).

  1. hiking_exposure=safe
  2. hiking_exposure=caution
  3. hiking_exposure=exposed
  4. hiking_exposure=fatally_exposed

This better and less likely to need look-ups in the wiki to figure out what each value is supposed to mean.

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we probably need a default value, and to decide if no tag means “safe” or “unknown”.

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what I like most in your proposal is the psychological dimension: how a typical person sensitive to heights will react. It may prove difficult to standardize and to gather data, but I feel it’s what we need.

However, although the words you propose are clear and simple, I’m afraid they tend to drop the psychological dimension. “safe” can be interpreted as an intrinsic quality of the path.

The Skywalk at Grand Canyon is definitely safe (or so I hope). Still, I know some good hikers who could not walk it. If we keep “safe” as a possible value we can expect many contributors to make the confusion and use it for the SkyWalk.

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I would go with unknown. We can parse for sac_scale but that isn’t reliable as it combines multiple concerns (difficulty, angle, exposure, etc).

I’ve been on maintained dirt trails (T1/T2 technique) that had sections that were single width and a drop on one side and a steep upwards slope on another that were at least T4/5 exposure. Before the trail maintenance two years ago this trail at Lee’s Ferry had many people uncomfortable and some turning around.

“About 2/3rds of the way up is a little stretch with some exposure. The tread is about 9” against the wall with a couple hundred foot dropoff."

Yes that’s what I’ve understood from personal experience and talking with people doing “alpine routes”. I led an ex partner on her first XC backpacking trip - she was fit, experienced at trailed backpacking and hiking, but unused to dry loose terrain (being from the PNW) and exposure. She was literally in tears, frozen, on what I would consider use_of_hands and use_caution terrain - probably a 1m drop down from some boulders onto a soft but poor traction surface. I didn’t even think about it, it’s an informal path that NPS personnel will take hikers doing a supported “hut tour” type loop up so it’s not that scary (park personnel are very conservative when it comes to safety risks and the public). I really hesitate to call a 1m drop “somewhat exposed” but it is something worth mentioning.

When writing up passes a lot of times people will mention being very uncomfortable on what I’d consider exposed terrain where they are on a < 1m ledge with fatal exposure on the side. I was watching my footing, but wasn’t overly concerned.

I tried to add some “verifiable” information to give context to the perception based aspect, to help out. To be fair something as terse as SAC doesn’t mean really anything unless you’ve been on a lot of SAC trails: fall danger > danger of falling > somewhat exposed > exposed > very exposed, etc.

Yeah, safe was a quick on the fly wording - while this shouldn’t be directly commented on in-and-of-itself here. I honestly think of this category more as “fall risk” than exposure given that the first two values are unexposed, but exposure is the common term and they fit together cleanly.

I’m not sure I would classify the SkyWalk as exposed due solely to perception, exposed should IMO have some risk even if it’s not critical (see the < 1m ledge example). This unfortunately the depth of field is hard to make out, but this is the section of Sluggo Pass that came to mind as R / exposed for me. Orange is a cliff band 15+ meters high, blue points to where I routed.


scary_but_safe (walking on a glass floor, something with via ferratta protection, etc)
no_fall_danger (old safe, maybe just keep safe)
fatally exposed

There’s a nice term used in Western US mountaineering at least - airy. Not really casual friendly, I just like the feel/mood of it.

“Climb the first pinnacle and from the gap descend about 30 feet to a ledge. Follow this ledge around an exposed outside corner to the notch between the south and middle summits. Cross to the north side of the notch on an airy bridge and traverse across the east face of the middle summit to the notch between it and the north summit”

Excerpt From
The High Sierra, Peaks, Passes, Trails
R.J. Secor

In French : “il y a du gaz” (there is some gas).

Gorgeous, that’s a nicer image than me with a burrito after a hike. :wink:

I rewrote the proposal (heavily on 0-2, but I added matching risk/perception values on the other ratings).

In french (or maybe Swiss French), we also say “aérien”, the exact “airy” translation in the same context.

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And I can’t resist sharing an example. Difficult alpine hike, or easy climb. Definitely some gas.
Gerbier : Traversée des arêtes - YouTube (watch around 1’10")

As an example, here: “Un passage aérien permet ensuite de surmonter une paroi étagée.”

I live next to the Dent de Morcles and can definitely confirm that it is quite “airy”.

I was really impressed until I saw the rope haha (still a little impressed honestly). That’s definitely some fatal_exposure there and much more than I’d be comfortable doing unroped.

Some interesting examples elsewhere, it starts off with casual_walking, in the next few seconds has surefooted_walking with both no_fall_danger. The chute around 0:30 looks more like scrambling than use_of_hands and I’d probably put it at exposed vs short_falls_possible as it steepens up enough that it seems like someone just tumble down it.

This was a fun feature in Yosemite and about where my casual “hiking” / scrambling limit is. The majority is not as directly exposed as it looks if you wiggle around it and come from the back aside from the summit block and a few moves before it. I’d put the summit as fatally_exposed even though it’s not quite so knife edge as the previous video.

While this is not really the right place for feedback on the link below (temporary WIP website), the 3/4 PG here would map to short_falls_possible scrambling, 1/2 R would be exposed surefooted_walking to use_of_hands, and anything with X would be what I’d consider fatal_exposure at least on semi-technical level for off-trail hikers and backpackers. It’s geared towards a US audience so is based off of YDS. I basically copy pasted it over here, but it’s grown nicely since to fit a more casual & trail centric general audience. :slight_smile:

I have another set old photos I pulled out to parse for this but haven’t gotten around to.


I honestly don’t have a great intuitive feel for stuff below what I’d consider fatally_exposed as that’s the only thing that really gets me feeling like I need to be really sharp. It’s something I’ve been trying to be more aware of as I tend to downgrade exposure on terrain I’m comfortable on - I have to try and extrapolate out to what I would have thought when I was younger / people I know etc.

So… what if we just drop the term exposure and only mention it in value descriptions? 5 would be exposed, 6 fatally/severely exposed in mountaineering terms etc. It’s currently the following:

Rename the key to something like hiking_fall_risk (technically only the last two values really deal with real exposure) and values are:

long could be replaced with fatal.
short could be replaced with minor or moderate perhaps.

This would make more sense to the average person I think.

Actually 2 isn’t quite “no fall risk” as someone can trip and fall over a root or something on a surefooted_walking path. I think this is probably a more accurate way to describe things:

likely could be problematic, as a tourist is more likely to fall on fatally exposed terrain than a mountaineer, but I think that captures “direct exposure” vs “indirect exposure” in a more casual friendly way. probable perhaps?

There should be some way of showing that 5 is scary, you could possibly die, but you aren’t likely to - a 9" wide even trail with a fatal drop on one side etc. 6 should be something like “oh someone died falling there, that makes sense to me”.

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Would it be good to separate likelihood and consequence? It’s getting long. Eg maybe a small chance of fatality could still more dangerous than a large chance of slipping to light falls. The list makes it seems =moderate_falls_likely is a possible candidate, while it’s not yet.

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I’m not a mountaineer in any way, although we do go bush-walking (hiking).

When I started reading, it took me several paragraphs & looking at the Wiki link to realise you were talking about the risk of falling!

When I saw “exposure” I immediately thought you were talking about being exposed to extremes of temperatures (both cold or hot) & other types of inclement weather!


Two alternative options:

hiking_vertigo={low, high, extreme}

hiking_perceived_height=XXX (in meters)

I guess this is mapped here Way: ‪Traversée du Gerbier‬ (‪830726688‬) | OpenStreetMap ? This definitely is out of range of the sac_scale hiking scheme. It is not tagged such, rightfully.

If you asked me, highway=path is trolling there.

I see, you did away with “caution”, a term that I could immediately familiarize with. It did remind me though of a place where I said to myself, now you gonna watch your step, even though I did not feel exposed, it felt airy neither (luftig in German.)

The next day, a hiker fell to death in the very location, when she lost balance swapping sticks from one hand to the other. The path on OSM is a T3 and that seems about fine, as there are assistive ropes all over. It is a crowded place, lots of hikers out for the scenery. I talked with some of them. Coming straight from urban flatland, they can walk hours a day for over a week, but they hate mountain paths.