RfC Part 3: foot_scale=* (aims to describe global paths in a more helpful and informative scale than SAC)


The current sac_scale has… issues. The value names are too specific (people tag easy trails in the alpine as alpine_hiking, mountain_hiking can easily occur outside of mountains) and it’s geared towards mountaineers vs normal hikers and recreational walkers (half the values involve some form of climbing). Outside of some European countries it’s not well known at all, so there’s not any real value from adopting it globally (it can and still should be used in those places alongside this scale) and it doesn’t attempt to cover non Alps concerns.

Take 1 is here: RFC: hiking_technique key (or a better name!) to describe movement on paths by hikers and then grew too long for people to catch up on.

Take 2 went in a different direction (more of a walking_scale) but had some great insight: RfC: New Key foot_scale=* ("now for something a bit recreational") - #108 by Hungerburg

This take 3 merges the two while keeping more to the spirit of the first and is fairly well finalized. I’ll toss it up on a wiki soon (hopefully) with example photos.

Value 0: casual_or_attentive_FIXME


This value would exist for data ported over from the existing sac_scale T1, as there’s no real way to tell if the path should be either casual or attentive.

Value 1: Casual


Requires little to no attention to traverse, very accessible

The ground may not be entirely smooth and clear but it has few to no obstacles and is over flat or low angle terrain. If there are obstacles they are to be minor and/or have a large amount of space around them. These paths can often use imported materials for their surfaces (gravel or asphalt) but can also be on naturally occuring firm ground where traction is not an issue. The path must be wide enough for people to walk side by side and for people in opposing directions to go past each other without stepping off of the path. Steep drop offs must have a railing or some other means of protection.


  • Accessibility: In general anyone that can walk (even with some mobility issues) like those that need to use a walking aid, the very young and elderly, etc can safely traverse this terrain.
  • Focus: Little to no focus is needed, people can walk and talk and not pay much attention to the path surface.
  • Footwear: Almost all casual footwear will be adequate.

Roughly equivalent to local scales:Class 1 YDS, ~NFS Class 4-5 Trails, SAC T1 / Yellow, Austria Blue, CAI T, AWTGS Grades 1, PWS W1 & W2

Note: Casual walking paths that are wheelchair accessible should be tagged with wheelchair=yes.

Value 2: Attentive


Requires attention to traverse, but still relatively straightforward

These paths are generally are either narrow enough that people need to walk single file (and step off to pass), have steep unprotected drops offs along the side, or have modest yet impactful obstacles. Obstacles are generally ankle to knee high like roots or rocks - though these can almost always be avoided and it is possible to walk on an even or nearly even surface. The surface itself still provides decent traction regardless of obstacles, but you may need to pay attention in places especially if you are on a moderately angled slope.


  • Accessibility: People that need to use aids when walking, or have relatively minor issues that impact their mobility can have problems and need to move carefully, but should be able to safely traverse it.
  • Focus: People need to be attentive of obstacles or footing to avoid tripping or slipping, but can still split their attention to carry on a conversation.
  • Footwear: Sneakers or other casual footwear should be fine.

Roughly equivalent to local scales: Class 1 YDS, ~NFS Class 2-3 Trails, SAC T1 / Yellow, Austria Blue, CAI T, AWTGS Grades 2, PWS W1 & W2

Value 3: Surefooted


More complex terrain that requires surefootedness to traverse

Where attentive path surfaces have obstacles that can largely be avoided, this terrain requires people to be able to move with balance and coordination (be surefooted) to maintain traction. It’s common to have to lift your legs high to step up onto an obstacle, or move from uneven obstacle to uneven obstacle like rocks or roots. It can also include moving through mud, wet clay, slick or loose surfaces, etc where the surface itself is essentially an obstacle due to poor traction. A path is also surefooted if it is obscured enough you can’t see where you are stepping, as you may need to react quickly if stepping onto an uneven or loose surface.


  • Accessibility: If someone has mobility or balance issues they may be unable to proceed safely or comfortably on this terrain. This can be very challenging to inexperienced hikers, but will be straightforward for mountaineers.
  • Focus: Attention will need to paid to footing for long stretches in places to avoid loss of traction or falling.
  • Footwear: This is more consequential. Lightweight but outdoorsy shoes like trail runners or approach shoes would be helpful, but sneakers should still work though more care might need to be taken. People with bad ankles or that lack experience may want traditional mid or high top boots.

Roughly equivalent to local scales: Class 1 YDS, NFS Class 1-3 Trails, SAC T2 / White-Red-White, Austria Red, CAI E, AWTGS Grade 3?, PWS T1-T2

Value 4: Hands for Assistance

Rougher terrain requires hands for balance, or to interact with obstacles


The path surface that is uneven or steep enough that it’d be reasonable to expect people to require use of their hands or trekking poles to safely traverse it. Obstacles like larger talus or boulders where you need to put a hand on a piece here or there to support yourself, aid with balance, or move around it. You might be occasionally be pushing off or pulling up on obstacles, but you aren’t actually using them to scramble or climb and you aren’t searching for mulitple handholds in a row. Having to actively push through bushes or branches to proceed as opposed to just brushing them out of the way occasionally would also fall into this category.


  • Accessibility: You need a stronger sense of balance and coordination than on surefooted terrain. Being able to control your body’s momentum and be aware of your weight and how it is moving over obstacles is important.
  • Focus: Intense concentration is often necessary. The skill and experience to think a few steps ahead while focusing on the path is very helpful.
  • Footwear: At this point something with grippy soles meant for hiking is highly recommended. These can still be very lightweight for experiened individuals.

Roughly equivalent to local scales: Class 2 YDS, NFS Class 1-2 Trails, SAC T3 / White-Red-White, UAII 1, Austria Black, SWW White-red-white, CAI EE, AWTGS 3-4?, PWS T3-T4?, BMC Grade 0.5?

Value 5: Scrambling

More vertical terrain where hands are used to climb/scramble, but is simpler than technical climbing=*


Obstacles: High angle obstacles that need to be “climbed” finding handholds and footholds and pulling oneself up, but are simpler than technical climbing=* which use of a rope and harness are expected. Feet are off the ground for more than a few moves, or there are repeated sections of short climbing.


  • Accessibility: You need to be able to pull up your body weight with upper body strength. While not considered “technical climbing” significant risk can be involved. Previous climbing or mountaineering experience is highly recommended.
  • Focus: Loss of focus can have lead to serious or fatal consequences.
  • Footwear: Something a bit technical is recommended. You’ll generally want something more traditional with “structure” or a lightweight shoe that conforms to the foot for better feel and independent use of foot muscles for control.

Roughly equivalent to local scales:: Class 3 YDS, Bouldering VB, NFS Class 1 Trails, SAC T4-5, UAII 2, Austria “Alpine Route”, CAI EE, AWTGS 4-6?, PWS T3-R?, BMC Grade 1-3

OSM Mapper Note: Some hiking systems overlap into technical climbing - SAC T6 regularly covers extended UIAA 2, YDS 4 goes into the lower range of Class 5, etc. These are far closer to technical climbing routes than recognizable paths that people can follow on foot, and are not appropriate for this scale.

Just marking a section of a path as a scramble is useful. More technically minded people can add on a local scale to help differentiate grades of scrambling - BMC, YDS, SAC, etc.


This is the last thing that I’m very unsure about. I can see this going a few different ways, each with their own merits and drawbacks:

  1. scramble covers all possibly applicable grades: YDS 3-4, SAC 4-6, etc.

This is simpler, but also puts what should arguably be climbing routes (and are treated as such more often than not) as “paths”. Many European countries won’t put T5-6 on maps, and a T6 “path” often has no visibility and consists of UIAA I to II terrain, which in my mind is less of a path than a route. I’m also coming at this from a western United States standpoint, which is no more or less valid than another. This does seem to line up with many international standards (Australia refuses to map it’s hardest level routes as paths, and many other European countries do as well).

  1. scramble only covers lower non-technical grades: YDS 3, SAC 4-5, etc.

This could be strange for some countries (UK, Austria, etc) that do show such routes on maps. There’s nothing to stop someone from tagging a climbing route as sac_scale=difficult_alpine_hiking in countries where that is the norm. That said it could be awkward in the UK, where there is a dedicated three grade scramble scale that would probably have the top value lopped off.

It’s pretty easy to argue that UIAA II isn’t really traveling “on foot” anymore.

  1. scramble could vary from 1-2 on a country (or regional basis)

Have scramble be a sort of “what is regionally considered a path that you scramble on”. I think the majority of places will fall into 1, at least for formal paths. Most informal paths that sections on the lower end of technical have poor enough visibility and/or are steep enough that a mapped line isn’t going to help you much if you can’t personally routefind from A to B anyways.

This makes the tag a bit more ambiguous, but I feel like having a local yds_scale, sac_scale, bmc_scale, etc alongside it for the technically minded folks that are interested in scrambling would balance that out.

  • 1 - lower scramble grades are path, higher that overlap climbing should fall under that key
  • 2 - all semi-technical and lower technical scrambles are paths
  • 3 - have this vary by region
0 voters

I’m putting down a vote for #1 with the caveat that foot_scale=scramble is unlimited for ways that are highway=path and that technical climbing should not be highway=path. If and only if a way is considered to be a non-technical hiking trail/path then foot_scale=scramble is the top of the the difficulty scale. If it ventures into technical climbing then a foot_scale=* value above foot_scale=scramble would be a troll tag and naive data consumers that don’t evaluate foot_scale=* would do a disservice to blindly render such ways the same as paths.

I would still support pulling out higher-difficulty scrambles into their own top-level tag key or value (e.g. highway=scramble or climbing=scramble), but in the other threads we’ve now documented many cases of common non-technical hiking routes that have scramble portions. The top key in foot_scale=* needs to cover the most difficult thing that would legitimately be tagged highway=path.

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Congratulations @erutan for this result! I’ve not been able to rejoin the discussion after I went for a hike :slight_smile:
Maybe the Value 5 description needs a bit clearer wording: reading “Feet are off the ground” and “You need to be able to pull up your body weight with upper body strength” makes me imagine one is required to pull oneself up by the arms only, like when using a pull up bar. I think what is meant is that the strength of both arms and legs (but mainly legs) is needed for this scale?

I suppose it has also been discussed how to implement this new key. Can you summarise it? Will this key replace the old sac_scale key? By automated replacement of sac_scale=hiking with foot_scale=casual_or_attentive_FIXME, etc.? Maybe Switzerland needs a special treatment: there will be many cases where paths there are tagged with sac_scale=* because that’s what they have been judged to be by the SAC itself. So paths in Switzerland could have both a foot_scale=* tag added by an OSM mapper and a (verifiable!) sac_scale=* tag, now redefined as “hiking difficulty according to the SAC”.

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That would make extensive routes across UIAA II terrain suitable for foot_scale, as it would top out much like sac_scale. Mind you: That covers scrambles over pathless terrain, in the colloquial sense of path.

Am I right that #1 in the text is #2 in the poll and #1 in the poll is #2 in the text?