Feature Proposal - RFC - Snow chains

This Proposal includes:

Tags related to snow chains:

  • Restrictions on roads regarding snow chains, with optional applying conditions and if they are variable (not active throughout the whole year)
  • Places to put on/off snow chains (which are dedicated and maybe parking restrictions apply)
  • Vehicle properties “snow_chains” and “winter_tyres” for conditional tags


The proposal was hibernating for nearly a year and I want to get it finalized soon. Please comment on things that need to be changed to get it ready for voting.

This RFC is cross posted on the Tagging mailing list (see archive: [Tagging] Feature Proposal - RFC - Snow chains).

You can discuss this proposal on its Wiki Talk page or on the mailing list or here.


Thanks for the update. I would definitely support the proposal as there are a few places in our alps where this applies.

Do I understand it right that “highway=chain_up_area” should not be used anymore? Instead the amenity=chain_change_area?

I am happy to share my experience from Austria:
In our country, the chain obligation is usually called spontaneously when snow falls. Translated, it looks like this for us:
“L198 Alpe Rauz - Warth between Alpe Rauz and Lech in both directions snow chain obligation, for heavy vehicles over 3.5 tons, passenger car winter tires”.
"B188 Wirl between Galtür and Silvretta Hochalpenstraße in both directions snow slippery (or icy road?), snow chains mandatory "

The messages are thereby shared via the public radio / news or the automobile club ÖAMTC. The messages usually do not have a time period. There is also usually only a warning when the snow chain obligation starts and not when it ends again.
Various additional signs are also used. (Sorry that these images do not come from Wikimedia).

-Deleted copyrighted images-
The additional sign only says “Today”.

-Deleted copyrighted images-
Here it says “Excluding motor vehicles up to 3.5 tons with winter tires”.

Other additional signs may include:

  • “Excluding all-wheel drive vehicles / 4x4 vehicles”
  • “Only in case of icy roads and snow”.
  • “Excluding passenger cars and station wagons with M+S tires”.
    ** M+S are special winter tires.

By law, all drivers of vehicles over 3.5 tons are required to carry snow chains between 1. Nov and 15. Apr. From this point of view, the tagging “snow_chaing=carried” would have to be completed with a conditional with weight over 3.5 tons and date range:
snow_chains:conditional=required @ snow; required @ ice; carried @ (Nov 01-Apr 15 AND weight>3.5)
(I hope I don’t have a knot in my head now.)

snow_chains:variable=weather would then be obsolete from my point of view, since this is already expressed by the conditional using ice & snow, or? Or is this meant as a combination?

Yes, I changed it a) because “highway=chain_change_area” collided with other “highway” uses, and b) there are chain-up and chain-down/off areas. See Discussion Chain down area

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Fine summary! Would be great if you could contribute it to the Additional Information subpage.

Variable means, that the sign is not always visible and will be shown variably for certain reasons, in this case only “weather”.

Please check the sections Rationale and Subkey snow_chains:variable=*. If you find it easy miss or to missunderstand, I’d be happy to get your opinion.

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Minor nitpick, but “chain change area” doesn’t really make sense. People usually aren’t changing their chains, they are putting then on and taking them off depending on the conditions. With the exception of maybe heavy goods vehicles, but they are the rare exception. A clearer tag might be amenity=chain_install_area, but then that doesn’t cover when they are being taken off. But regardless I think that’s what it’s usually called when someone puts on/takes of snow chains.

(BTW, the message was meant for @trapicki but replying to messages is apparently a little wonky)

I agree. In Austria they are named (and sometimes signed) with “Kettenmontageplatz” which would be in english something like “Chain assembly place” or “Chain mounting place”.

This is full intended and has some history. We started with chain_up_area and ended at chain_change_area. See Discussion about Chain_down_area.

I clarified that in the proposal.

Would “chain fitting” describe both installation and uninstallation less awkwardly?

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In colorado, usa, our dept of transportation is calling them chain-up stations, or chain stations.

Either amenity=chain_fitting or amenity=chain_station would be an improvement. Probably amenity=chain_station is the better of the two.

We have only a few people contributing to this discussion, therefore a personal preference is good, but we should objectify the decission. Multiple persons have statet that chain_change_area feels awkward, which is for sure enougth to have another look at it.

Nevertheless we need something that will work as tag both for simple cases, occasional mappers, and complicated situations. It should be robust enough for that.

Keys and values are codes and mnemonics, but not exact descriptions. Code means that in other contexts it could mean something different, but here in OSM something very specific, well understood and documented. We could just use numbers for that purpose. Mnemonic means it’s easy to remember (better than numbers…). highway=path seems paradox but works great for OSM. At the same time it should not collide with some common meaning of a term and lead to misunderstandings. to chain down seems to spark associations with to bolt down, not helpfull here.

For this snow chain manipulation places, different countries have different names. Moreover they come in different flavours, from lanes that can be dedicated to that purpose, sections of road shoulder, bays, and separate areas. Size can vary from suitable for a single vehicle and very short up to dozen of vehicles and stretching for several hundred meters.

Usually, we would use the British English term, but I have the very strong feeling that there are no such places in the UK, even in Scotland snow seems to last not long enough for people to bother evena about snow chains.

Some things have different names for complementing aspects of the same thing, like entry and exit. It would be preferrable to have a key that combines that in a generic way that does not preclude one of the aspects. Then we can establish more tags that resolve that to more specific aspects, providing a better structure and more flexibility. Most of the proposed names include area, which is most of the time fine, but also leads to colissions and less flexibility.

It would be nice if related tags can be identified/assigned by their name. Here, chain seems not enough, as this could mean many different types of chains.

Finally, it should not be too long and complicated, or it gets awkward again.


  • Not entirely awkward
  • Mnemonic: Ease to understand and remember
  • Generic, not necessarily an exact description or regular used term.
  • No collision with different denotation
  • Relatable to then main topic.

Something that a former Californian proposed to me in a personal discussion is snow chain stop. It sounds strange at first, but I like it for many reasons:

  • the connection to snow chains,
  • being not a used term and thus not favouring anything,
  • being generic,
  • not denoting an element type (node, way, area),
  • and including something that you have to do anyway, that is stop.

It parallels to bus stop and rest stop.

Including the Wiki Discussions Chain down area and Object type to use we have the following proposals:

proposal awkwardness mnemonic generic colission assignable
amenity=chain_up_area - + - + ~
amenity=chain_up_area, amenity=chain_down_area - + - - ~
amenity=chain_up_area, amenity=chain_off_area ~ + - + ~
amenity=chain_change_area, chain_change_area=*, chain_change_area:lanes=* - + - - ~
amenity=chain_up/chain_down, chain_up=only/designated/yes/no - + - - ~
amenity=chain_install_area + ~ - + ~
amenity=chain_mounting_place - ~ - + ~
amenity=chain_station ~ ~ ~ ~ ~
amenity=chain_fitting ~ ~ - - ~
amenity=snow_chain_stop ~ + + + +

For voting, I do not want people to start the discussion over again, so let’s find something agreeable, the thing where the least number of people could identify serious problems.

I assume that is partly in reference to the options amenity=chain_fitting and amenity=chain_station. Which is fair enough, I guess. But what other common meaning in the context of people driving along a highway through a snowy area has to do with chains except putting on snow chains? The only other scenario even slightly similar involve chains would be something like a heavy goods vehicles tying down their load, which is sometimes done with chains and sometimes not, but no one refers to that as “chain fitting” and there aren’t dedicated “chain stations” for it either. Just regular truck stops. So unless there’s some scenario I’m not aware of I don’t really see how amenity=chain_fitting and `amenity=chain_station’ would cause anyone confusion. Although, I don’t think it that big of deal if there’s confusion anyway since we still use potentially confusing tags regardless (whatever=bicycle for example when a bicycle can mean an extremely wide range of things to different people. Even in the UK BTW).

Somewhat tangentially, no one dialect of English is perfect. The principle you’re referring to is more about preferring British English spelling and avoiding conflicts with British English usage, but not necessarily pondering a hypothetical Britain with a different climate or restricting ourselves to what most Britons have words for. The classic example (not entirely accurate) is that we came to prefer the American term sport=soccer over the British term sport=football due to massive confusion with other footballs. At the time, I don’t think anyone seriously considered coining a novel descriptive phrase just because we couldn’t use the British term “football”.

That said, I don’t think any of the options in your table would noticeably hinder adoption by mappers or data consumers. Whichever one we end up voting on, there’s still going to be a followup discussion in the id-tagging-schema repository about the field’s name and aliases in American English (which for better or worse is the default English dialect on the Web platform), and then translators will have an opportunity to customize the name and aliases for various locales, including British English. The aliases will be important, because some people who aren’t familiar with these facilities may think of analogies like bus stops or fitting rooms.

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