About & Thoughts

Order of Operations

Class (1-5), then terrain aspects (S, L, C, or B), and finally fall risk (PG, R, or X).

Terrain that you slide around on and is exposed on uneven/steep ground would always be 2 S R, not 2 R S or R2S etc.

Overview (what and why)

The Yosemite Decimal System has been in use for decades and is the default way of rating mountainous terrain. It was created and used by technically skilled mountaineers, and since then most of the attention was spent on the top of the scale (Class 5) leaving gaps in describing Class 2 and 3 terrain that are significant for backpackers. This is a proposal for a more inclusive system which builds on it's historical roots while being useful for a wider range of individuals.

The largest change is the addition of a “Class 2.5” which clarifies an ambiguous grey area between Class 2 and 3. Existing 2.5 terrain would most likely be rated Class 2 by climbers or mountaineers who didn't consider it “easy climbing”, and Class 3 by backpackers who weren't expecting to have to use both hands to pull or drop themselves and their heavy packs down what was promised to just be uneven ground.

The second change is the addition modifiers for terrain aspects (Loose, Collapsing, Skidding, and Bushbashing) and fall risk (PG, R, and X). One can easily come up dozens of useful ways to describe terrain - this an an attempt to include only the most pressing aspects. The main advantage of this system isn't having a rating that perfectly describes reality (it doesn't), but creating a clearly defined shared vocabulary so descriptions of terrain are (not as) subjective and.

Similar to how Class 5 is ordered by the class rating, grade, and risk (e.g. 5.10c III PG), classes 2 through 4 will be class, terrain aspects, and then risk (e.g. 2 S R).

Unpacking ratings

It'd be useful (when not in a table or chart of passes etc) to unpack the acronyms into "human readable" language. At this point I don't think this needs to be formalized as long as all the longhand terms are used.

Ursula

Class 2 X, 3 R - Some fatally exposed uneven ground and exposed simple climbing

Class 2 X, 3 R - Uneven ground fatally exposed and simple climbing exposed

Vernon

Class 2 L, 2 R, 2.5 - Uneven ground loose, uneven ground exposed, short mantles/drops over rock

Class 2 L, 2 R, 2.5 - Uneven ground, sometimes loose or exposed with some short mantles/drops over rock

Approach aspects that don't show up in a rating

These will come up when viewing a pass, but aren't a terrain or exposure modifier to help keep things simple.

Snow

I think listing approaches that generally hold snow is useful. Even if Sentinel 2 satellite passes reduce this a bit, seeing a pass that historically held snow all summer dry is a warning that the terrain underneath could be unstable.

Traction recommended

Not as reliable in this day and age of climate change, but it's worth flagging the old old Secor "Ice Axe & Crampon" required on passes. If there is snow this indicates it needs to be taken serisouly. If not it's a similar but stronger warning than the above.

Prefered directionality

Sometimes a set of approaches make much more sense one way than another (e.g. some airy class 3 on one side, a sandy slog on another).

Tricky routefinding

Cirque comes to mind here, it's a straightforward pass... if you don't make the really common routefinding mistake that most do and end up on a series of wet class 4 cliffouts.

A brief overview of traditional YDS

According to Secor (he goes into more detail, this is his initial brief introduction, it's well worth owning your own copy, the third edition is the latest):

Class 1 is walking.

Class 2 is defined here as difficult cross-country travel. In the High Sierra this is usually talus hopping, which requires the occasional use of hands for balance.

Class 3 is where the climbing begins. Hands and feet are used not just for balance, but to hang onto the rock. Steep or large talus can be rated as class 3.

Class 4 is on steep rock, with smaller holds, and a lot of exposure.

Class 5 is steep and difficult rock climbing, involving the use of protection placed between the leader and the belayer. I differentiate class 4 from class 5 by the hand- and footholds. Class 5 requires obscure holds [...]

Another way of differentiating between classes (which is intuitive if overly simple and lacking in nuance) is the points of contact system, counting rope as a point of contact (I didn't come up with it and don't think it's better than Secor, but it's simple).

C1 = feet

C2 = feet + 1 hand [or trekking poles extended/contracted, used on steep or loose terrain]

C3 = feet + 2 hands

C4 = feet + 2 hands + rope (recommended)

C5 = feet + 2 hands + rope + elaborate means of protection

For more Class 5 centric reading there's great long form articles on Climbing House and REI.

Why not just use the SPS Scrambler Rating System?

It's well thought out and more informative than traditional YDS, but IMO makes the same mistake of YDS of combining exposure with terrain aspects and modes of travel into a single rating.

I've been on terrain that would be 2.0 according to their rating in terms of difficulty but had fatal exposure - is that a 2.2 due to exposure, even if it's a straightforward 2.0 slab walk? You can try and parse down "risk" as being tied to a fall being less likely on easier terrain, but I think just listing exposure is simpler and fits how people think of terrain better.

Tying routefinding into ratings makes some sense, and works in most cases, but there are spots that can be more technical (or risky) but obvious in terms of route finding. There's passes where a lot of people end up on Class 4 instead of 2 due to a poor choice 2/3 of the way down (looking at you Cirque), however the SPS system doesn't let you know if routefinding is the critical aspect due to everything being smushed together.

One thing I like about my system is that it makes it clear when class 2 is less desirable than class 3 - I haven't done King Col but despite it being Class 2 it has loose fatally exposed terrain. Something like Valor pass which is a bunch of slabs with a super simple fat crack of short class 3 sounds infinitely more welcoming.

Having King Col at 2.2 and Valor 3.0 in their system makes sense in terms of difficulty, but that puts the risk of injury at the same level on both... which isn't true at all! Comparing 2 SX and 3 makes it lot clearer. It's not unusual for me to choose to do some stable 3 over loose 2 when I get the chance. Desirability of terrain isn't linear according to technicality of movement.

The breakdown into 0.1 and 0.2 systems is very thoughtful, but also feels like it can get into trouble - I don't carry a theodolite with me when I'm backpacking and route finding can change the maximum angle of things. Just stating the general type of movement over terrain (1, 2, 2.5, 3, 4) makes sense combined with standout aspects of terrain (S/L/C & PG/R/X) to me as people can look at modern maps with slope angle shading and get a feel for the steepness of a pass. It's also less subjective than what people "feel" a section is in terms of simplicity of holds etc.

The fact that length of the approach is factored into the rating feels a bit wrong to me as well, that should be apparent just by reading topo especially now with slope shading overlays on major mapping clients. Pilot Knob is similar to Observation Peak (and definitely requires a bit more technique and is more exposed than Midway) but it's rated as 2.1 and the other two are 2.2.

Origin & Feedback

Starting from this post on High Sierra Topix there's been some good conversation on the evolution of this system.

I'll be starting a new thread on HST when this site is a little more functional - if you're proficient with git and markdown feel free to make a pull request, or just put comments into the issues section of the Github repo.

Some Example Pass Ratings

King Col: Class 2 S X.

This pass should not be taken due to uncomfortably slippery terrain over fatal exposure.

The technique required is to move over steep and/or unstable ground using hands (or poles!) for balance. That's Class 2. The fact that if you slip you die or get medivaced out instead of just falling on your ass is because it's fatally exposed. The fact that your feet will slide when you step above that fatal exposure makes it sliding. This is why people say King Col feels like Class 4 - the proximity to the drop makes it 'feel' like you're on a more technical climbing mode of travel because near vertical terrain has a lot more high cliffs than terrain 5-30 degrees in slope. 2 SX 'feels' like 4 because it's exposed, not because you need to have good shoes and know how to move on rock with small holds that require some climbing techniques.

Cirque: Class 2.5

North side: Straightforward class 2 with some 2.5 near the top. South side: 2.5 ledges near the top with routefinding (or more directly short class 3) on the south side followed by significant routefinding that can mean the difference between straightforward class 2 & 2.5 and wet class 4 near the bottom.

Rodgers: Class 2 C

The upper west side of the pass is composed of talus that require significant routefinding and situational awareness to stay safe on - landslides can occur 30 feet upslope of where a step is taken and sweep down onto the hiker.

Valor: Class 3.

Straightforward mix of slab, broken slab, and very occasional talus with brief Class 2.5 and Class 3 sections to gain/drop from the ridge from the east.

Vernon: Class 2 L, Class 2 R, 2.5.

East: Straightforward mixed 2 until the last two hundred feet which are a mix of occasionally somewhat wobbly talus and optional stable 2.5/3 sections to an exposed feeling wide talus ledge then some routefinding for a 2.5 path through 4. West: Mix of generally stable talus and rolling slab, and varying amounts of 2S depending on routefinding.

Note: the sliding and exposed sections for this are in different sections, so it's not really 2 SR but 2S & 2R. Kind of awkward.

Lamarck Col: Class 2.5

East: Well worn use trail until the base of the col, which generally holds snow (or ice) mixed with stable talus year round. West: Straightforward Class 2 mix of stable talus and a sandy slope, with almost certainly some 2.5 moments near the top. Worth noting that the large talus along Darwin lakes 2 & 3 is more of an obstacle than the pass itself!

North Col: Class 2.5/3.

Class 2 from the east with either 2.5 or straightforward 3 at the top depending on time and effort spent on routefinding. West side is 1/2.

Dragon: Class 2 L, 2.5.

Ursula: Class 2 X, 3 R.