Talk:Tag:traffic sign=city limit

Ambiguities : city limits within the same urban area, entry/exit, application of restrictions, effective boundaries...

There are cases where city limit signs are present within the same urban area, when going from one city to another. In this case there are usually (but not always) two signs on top of each other : one for marking the exit of one city/town/village, another marking the entry to the next city/town/village.

As these signs imply driving restrictions such as speed limits, it is not clear if this marks the end of the restriction. As well, marking only a node (usually on a highway or frequently just beside it) does not clearly indicate on which part of the highway the restriction applies.

Frequently as well, you'll find an entry sign in one city, but the exit sign will display another name (or the same name with distinct precisions added): this is frequent in rural areas where the same small village is split into several parts belonging to distinct administrative units. Which value should we indicate for the name ?: if the traffic sign includes a precision, it should be present, but the complete name will not match any place name, as it will be composite, e.g. (this layout looks like a French agglomeration entry sign, with a smaller yellow sign on top, for the highway reference number):

D 108A STE-VILLE-SUR-NAME1	.......	D 108C VILLAGE-LOCAL-NAME2 Commune de STE-VILLE-S/-NAME1			D 108C VILLAGE-LOCAL-NAME2 Cne de L’AUTRE-VILLE-S/S-NAME3	.......	D 108E L’AUTRE-VILLE- SOUS-NAME3
in 1st agglomeration (main)		in 2st agglomeration (exclaves)					in 3rd agglomeration (main)

Note that the precision of the commune shown in italic and smaller font below the local place name may be partially abbreviated or lowercased (in some cases, the main place name may also be abbreviated or shown in smaller fonts on common words like "SAINT", "LE", "DE"; however the most significant words in the local place name of the agglomeration will be capitalized; local place names in non urban areas such as hamlets are not using this emphasis and don't even use the same colors as they are purely informative and they imply no change in driving restrictions: they are not "city limits")...

This would give the tag "name=Le Village-Local-Name1 (commune de La Ville-Name2)". If you look for the administrative place name (commune), you'll find only "La Ville-Name2" (in this example), but the urban area of "La Ville-Name2" itself does not include this part of "Le Village-Local-Name1" which could be exclaved. Note that in such villages split onto several municipalities, there's frequently no city limit on their separation which may be in the middle of the same urban street (this case occurs on small agglomerations with houses all along the same single axis, or the separation is on a bridge over a small river or on a minor cross road; house numbers are not necessarily discontinuous, and the street/road keeps its local name or reference number) ; the toponyms on city limit signs may remove hyphens and long names may wrap on several lines.

Finally note that not all highways may have these signs (minor roads for agricultural use or driveways with private/restricted access may cross these limits without any explicit markup and there's not necessarily those sign at end of these private/restricted highways).

The tag also does not explicitly differentiate the entry and exit signs (which may not always be located at the same place on a bidirectional highway): I suppose that this tag is only relevant for the entry sign (if there's no entry sign in one direction, but there's an exit sign in the other direction, we could place the tag there as if it was an entry sign).

For these reasons, the speed restrictions (or other applicable restrictions) should be explicitly set on relevant segments of highways (using limits of landuse=residential/commercial/industrial would be very unreliable as these landuse are frequently different from the legal boundaries marked by these signs).

Some contributors may also want to create true boundaries (relations) for "urban areas", but there will be a confusion with urban areas created in official national statistics: the local municipalities may decide to apply restrictions differently along some highways, by placing such city limit signs elsewhere than an the official urban area. As well there are frequently several types of urban divisions in national statistics data (and each country may use their own definition of these statistical or economical urban boundaries for different purposes: "urban area", "urban zone", "agglomeration", "urban pole"...).

So I just suggest that this traffic sign tag only indicates the visible physical presence of the traffic sign, and no other interpretation. We should not need this tag for delimiting restrictions, or any statistical/economical boundary: as it is, this tag is merely and only informative, but unusable in practice for anything else than at the node itself (just like the admin_centre node in boundary relations) as we cannot really determine its applicable area.

Ideally this tag should also indicate from where it is visible, but unfortunately the tag indicates no orientation (and it is not clear which direction to indicate: facing direction to the viewer, or direction of application, or anoother direction if the sign is placed beside the road)... The description also does not explicitly states if the node should be on the highway (often virtually) or beside it (more realistic on the ground, except if it is suspended above the highway, and nothing about the type support: on a vertical pole, attached to the trunk on a tree or fixed on a side wall, or below a bridge or entry of tunnel, or suspended on a cable...)

Map renderers may exhibit some icon, but its interpretation will still be left to the viewing human. Most renderers will simply ignore this tag.

— Verdy_p ^(talk) 01:41, 21 August 2016 (UTC)

direction

I think this tag would benefit from the direction key. But should it point into the city or the opposite way?
I would say it should point into the city.
--TBKMrt (talk) 21:12, 3 February 2018 (UTC)

I agree that this can benefit from direction. For traffic signs, the direction is where the front of the sign is facing, see the drawing from the accepted proposal (the stop sign example). Typical city limit signs face away from the city. --Tordanik 13:28, 4 February 2018 (UTC)

In some countries you have signs when you enter the city and on the other side of the pole there is a sign that you leave the city (including no longer existing speed limits etc.)

But since driving into the city is more important the the other direction and a check for a 180° rotation can be done by the navigation system (rg. entering the city is the other way, so I am leaving) I would agree on the direction tagging here.

--TBKMrt (talk) 20:59, 6 February 2018 (UTC)

Since there was no further comment on this I include the direction tag with an example image. --TBKMrt (talk) 22:50, 22 February 2018 (UTC)

The page is not 100% clear as to which way 'direction' should point: into the city or outside? From https://wiki.openstreetmap.org/wiki/Key:direction#Examples , I'm inferring it should point outside (the sign affects inbound traffic, thus it points out). If this is confirmed, can we state that explicitly on the wiki-page, please? Note there's a similar question here: https://wiki.openstreetmap.org/wiki/Talk:Key:city_limit ... so I'm not the only one confused. SmootheFiets (talk) 12:11, 28 July 2020 (UTC)

After checking with the Dutch and German forum (who agreed I had it backwards...), I've taken the liberty of adding some text to the wiki explaining which way direction should point. --SmootheFiets (talk) 09:55, 14 August 2020 (UTC)

Sorry, but for me this didn't make things clearer; quite the contrary. Lets go step by step. Please, tell me where you disagree.

1. traffic_sign=city_limit is a traffic_sign, so it obeys rules for other traffic_signs and direction usage guidelines. We must not give contradictory descriptions here and should not copy them from those master pages risking to produce a garbled version.
2. "Beginning of a city" and "end of a city" signs may or may not be installed on the same pole, so one may want to map only city beginning, only city end or both with one node.
3. "traffic_sign=city_limit + city_limit=begin" is the sign with city name (not struck out). It affects only inbound traffic, and its direction is away from the city.
4. "traffic_sign=city_limit + city_limit=end" is the sign with city name struck out. It affects outbound traffic, and its direction is into the city.
5. "traffic_sign=city_limit" without city_limit=* or with city_limit=both tag denotes two signs and is the only case that requires clarifying of direction meaning. Before your edit I had have liberty to resolve the ambiguity in favor of "begin" side of the sign, because my research revealed that it's common practice to imply "begin" face of a double-sided city_limit sign when thinking about direction.
6. I think mentioning of forward/backward direction values is improper here, since they are discouraged for end nodes of ways which is often the case for city limit nodes. I think it's better to give the direction value determination procedure away to direction wiki page.
7. Also, the direction of a city_limit traffic sign does not depend on how the node mapped: on a highway on next to it. From your explanation it looks like it does.

Waiting for reply, -- Alexey.zakharenkov (talk) 17:07, 14 August 2020 (UTC)

Thanks for your thoughts! Let me reply point by point.

1. I did, of course, not mean to provide contradictory advice. I'm reasonably convinced that I didn't (see below). But your point on not duplicating information that belongs elsewhere is well taken. "My" text is clearly too detailed for this page.
2. Again, point well taken. In my area, I haven't come across a single case of city_limit=begin/end; Overpass just tells me the nearest occurrence is > 100km from home. So, I didn't think of those. Maybe I should've.
3. Here's where it gets interesting: which way does a sign face? I agree with you that traffic affected by a city_limit=begin sign is inbound and that the sign is facing outward. As per https://wiki.openstreetmap.org/wiki/Key:traffic_sign (subsection 'As a separate node'), direction should be which way the sign faces, i.e., out of town. So, I agree with you for city-limit signs mapped as separate nodes. I disagree with you for city-limit signs (or traffic signs in general) that are mapped "as part of a way". As per the same wiki page, direction now means "the direction affected by a traffic sign relative to the highway=* way". So, that would be inbound!
4. See above.
5. I'd agree with you that city_limit=both (or not set) should be treated like city_limit=start as far as the direction tag goes.
6. I mostly disagree. forward/backward is the preferred set of directions for nodes that are part of a way; giving direction in degrees or cardinal points would not be robust against changes in way geometry, forward/backward is. This reasoning would not be true for nodes placed next to the way, but not on it. Where traffic signs should be mapped, on a way or next to it: that's a different question and a controversial one. We appear to be on different sides of that divide. But that's OK, let's not argue this here. Both have their pros and cons, both appear to be accepted by the community. You are right, of course, in saying that forward/backward are ill-defined at end nodes of a way. It's also true that many traffic signs including city_limit tend to be at the end of a way (because some tag or another changes, notably maxspeed). My solution is what's recommended on the traffic_sign wiki: "Avoid junction nodes and nodes between two ways as well (where they have been split, but are connected by a node). If in doubt, better simply insert a new node into the way instead of using an existing one." I tend to insert city_limits, like, 1m off the end of the way, where direction=forward/backward is well defined.
7. Well, I'm afraid it does matter. It's very regrettable that conventions should be this confusing, but that's how I read the traffic-sign wiki: direction facing for signs off the way, direction of affected traffic (i.e., the other way round) for signs on the way. This is also how it's interpreted by fellow mappers, at least in NL and DE (where I've consulted the forum) and in surrounding countries as per the cross-checks I've performed using Overpass. I wish it wasn't so confusing, but I'm afraid it is.

I'm standing by for your reply. But I think we agree that the text here should be shortened drastically; for the use of direction, we should just link to the other Wiki pages. They might need some clarification, but that should be discussed there, not here.

Actually, while we're talking: it says "direction should be specified if it cannot be deduced from other tags and road geometry." I didn't quite dare delete the subordinate clause, but it doesn't make much sense to me. When can you ever deduce direction from other tags and road geometry? I can think of exactly one case: one-way streets with the city-limit sign mapped on the way. In that case you can't have city_limit=both, only begin or end. So, that should be tagged instead of direction. But I may be overlooking something. Can you think of anything? --SmootheFiets (talk) 23:50, 18 August 2020 (UTC)

Thank you for the detailed answer. Now I see the point of divergence. The original direction key proposal was accepted quite early - in September 2011. It described compass direction as universal measure and made not difference between nodes on/off a way. Note "...forward/backward. This usage is not documented in wiki..." author's remark. At that time the Key:traffic_sign page had no mention about direction at all. I think it was personal opinion or an accidental omission to list 3 tag pairs in the "As part of a way" section of the Key:traffic_sign page and not to mention cardinal directions/degrees method. Overpass-api provides about 1000 city limit signs that are part of a way with cardinal direction values (though forward/backward are used an order of magnitude more often). Personally I prefer NESW tagging both on separate and joint nodes for city_limit signs - with my own reasoning. Hopefully we agree on that, to the extent that city_limit traffic sign resembles other traffic signs, this page should redirect one to Key:traffic sign and Key:direction pages. What is different is that city_limit may have (and often, but not always, do have) two faces.

I've put "...if it cannot be deduced from other tags and road geometry" as a replacement to the statement that was not applicable to "city_limit=end" variant. Really, I meant city_limit signs with begin/end refining tag on a one-way road (examples are nodes 418244980, 418244981) which are not so rare. Some mappers hate redundancy so I thought that to remain only "direction should be specified" would have been provocative. On the other hand we can't forbid to use direction tag even if it seems unneeded for us in some cases. You may propose your variant of direction tag necessity clause, including to omit the clause. In any case now I incline to move direction meaning clarification for double-sided signs from "city_limit=*" to "direction=*" paragraph. Like this: "direction=* is recommended if it would help to determine the location of a city in respect to the sign. For traffic_sign=city_limit without city_limit=* tag or with city_limit=both tag direction refers to the city beginning side." --Alexey.zakharenkov (talk) 16:37, 19 August 2020 (UTC)

Thanks for your feedback! Interesting to see how this evolved with time; I haven't been involved with OSM for all that long. As for the text, how's this? I believe that should be a version we can both be happy with.

• Replace last sentence of intro with "Most city-limit signs are double-sided (beginning of city in one traffic direction, end of city in the other); single-sided versions also exist, typically on ways with oneway=yes."
• "How to map", leave first two paragraphs unchanged. Then
  • city_limit=* should be set if the city-limit sign is single-sided. If not set or city_limit=both, the sign is double-sided.
  • direction=* should be specified for double-sided city-limit signs to clarify which traffic direction enters city limits. Set the appropriate value, following the general conventions for traffic signs, for the beginning-of-town side of the sign (except if mapping a city_limit=end sign, in which case direction=* is typically not needed).

Next thing on my agenda would then be to work towards a clarification of the instructions on direction=* and on traffic_sign=*. Maybe you're interested in that, too?

PS: I've just mapped my first city_limit=begin sign :) https://www.openstreetmap.org/node/6532947908 --SmootheFiets (talk) 08:51, 20 August 2020 (UTC)

I'm not so long in OSM either, just digged wiki history ;)

I like all your suggestions except "(except if mapping a city_limit=end sign, in which case direction=* is typically not needed)". Please look at city_limit signs around the node 7833897386. More correct would be "except if mapping an as-part-of-a-way sign node qualified with city_limit=begin/end tag in which case the sign direction is clear".

Good luck with further clarifications. I'll connect if I feel the need. --Alexey.zakharenkov (talk) 01:13, 22 August 2020 (UTC)

Following this discussion about direction, what would be the best way to map two city_limit signs, one signaling the beggining and another signaling the end, but each one on one side of the road? direction=both was the first thing that occured to me, but here we have two signs, not one double-sided. --AntMadeira (talk) 23:41, 19 April 2021 (UTC)

direction=both is an improper value. I'm afraid there is no agreement about the best way. Reasonable options are:

1. If you think (like me) that it doesn't matters how many signs inform drivers of the city limit and how far from the road axis the signs are installed, you may model the signs with one node on the highway tagged traffic_sign=city_limit [+ city_limit=both] + direction=* where direction stands for the direction of the "begin" sign.
2. Or you may create two nodes off the road, one with city_limit=begin, the other with city_limit=end tag and with opposite values for the direction tag, e.g. N and S (for north and south). Alexey.zakharenkov (talk) 17:53, 20 April 2021 (UTC)

Since I don't like to map "offroad" signs, I'll follow the first option, but instead of using direction=* only for the "begin" sign, maybe we could use something like direction:begin=* and direction:end=*. What do you think? --AntMadeira (talk) 19:15, 20 April 2021 (UTC)

The direction tag may be applied to the end-of-a-city sign as well as to the begin-of-a-city sign by the same rules as for other traffic signs. A special case is a "city_limit=both" sign in which case one direction tag is still sufficient since the other direction would always be 180-degrees-rotated value of it. Even before (more probably - in unawareness of) the discussion of city_limit begin/end distinction, common sense suggested to put the direction of the "begin" face of double-sided sign for nodes tagged with traffic_sign=city_limit + name=* + direction=*, e.g. for node 4413876810. So, the proposed usage of the direction tag for city_limit is consistent with established practice. Alexey.zakharenkov (talk) 06:59, 23 April 2021 (UTC)

Mind you I'm not talking about doublesided signs, but two signs in parallel, one on each side of the road. direction=both would convey the idea that there is one sign (although doublesided, it's one node on the way) not two. --AntMadeira (talk) 15:08, 23 April 2021 (UTC)

When you collapse two city_limit signs located on the opposite roadside into one node on a highway way in OSM, you loose information about that there were two separate signs on the ground. In my opinion, if you want to reflect that fact you should map two nodes. I think a node(-s) beside the road should imply that the mapper mapped all signs carefully, and a node on a highway - that simplification was applied.

The direction=* tag on a city_limit sign should say in which direction one should go along the road to reach the city. direction=both on a on-the-highway node is applicable only if whichever of the two directions you choose you will come to the city. Alexey.zakharenkov (talk) 16:40, 23 April 2021 (UTC)

Rendering

Mention if rendered. Jidanni (talk) 18:58, 20 August 2023 (UTC)

@Jidanni: feel free to add rendering section. In general, posting some question on talk pages is useful but you do it at unusually huge volume, can you consider doing more research before posting? Mateusz Konieczny (talk) 05:48, 21 August 2023 (UTC)