Official classification of highways

General talk Tagging general discussion
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Hello,

in order to allow for a more consistent usage of highway=*, I’d like to propose global tagging of the official, national highway classification.

In some countries, highway=* already corresponds to the official classification, but that’s not the case everywhere.

Now, ref=* usually already shows what the road is classified as but sometimes roads can have no ref and in that case, noref=* doesn’t give any information. Sometimes, at junctions, roads can have small sections of no ref but still be managed by a certain entity so this would also be a sort of micromapping tag.

Some countries already have such tags being highway:category, highway:category:pl and highway:class:pl.

The tags mentioned above seem fine but there’s one detail I’d like to also contain in such a tag and that is the corresponding admin_level of the maintainer of the road. What do I mean by that? Most European countries have their roads divided into national roads, regional roads, etc. This is why I think it would be a good idea to tag it as such — national roads would be the value of 2, regional roads the value of 4 and so on. Aditionally, E-roads or a different continental network would have the value of 1 (and as always, the colon [;] is the separator for multiple values).

Some countries however, like the UK, don’t have a strict relation between the classification and the road maintainer, meaning they could probably use a different tag.

There’s also an official functional classification which oftentimes is just limited to motorways vs expressways and also needs it’s own tag — there is zone:traffic=*, but sometimes a road formally be a motorway or expressway before the sign, and having a new general tag for it allows to support countries with a full functional classification.

The reason why such tags would be useful is because some people might want to make a map where they have the official classifications instead of the subjective ones that are often present with highway=*. It’s also a way to fix incoherence because of borders in some countries without the loss of information.

My issue is that I just cannot think of the best tag names to make this scheme so I’m very much open to suggestions as well as feedback related to what I presented and if there are other complications with classifications globally.

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You seem to be talking about two different concepts here:

  • Official classification, broadly reflecting the role in the road network
  • Who maintains the road.

In a few countries there may be a direct link between these, but that is not the general case. So I would suggest not mixing these concepts as it is likely to end up in confusion.

For example, Ireland has official classifications called “national”, “regional” and “local”, but the latter two do not match admin levels “and are all maintained at county council level. I guess the entire road network could be tagged with just 2 admin level values but it seems rather uninteresting, of no use for routing, and probably not something people would expect to see in a general purpose rendering.

Even for a tag explicitly aimed at maintenance, using admin level numbers seems very restrictive. What if roads are maintained by some local body that does not correspond to an admin level? How do toll motorways operated and maintained by private companies fit in?

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Would it really not? That usually corresponds to something like 7 or 8.

In Poland such highways still have the same category and class but indeed there should be something precise like owner=* or highway:owner=*.

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Yes, and in the USA we have “national” road designations, but our national highway authority doesn’t do any road maintenance or operations. All maintenance and operations are handled at the State level or below, no matter which authority designated the route. Where nationally designated roads go through village centers, it is often the local town/village government that maintains them – potentially with partial funding from a higher level government.

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I believe operator is already used for this and works for different tiers of government as well as toll road operators.

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Indeed operator seems more suitable than owner in many cases, such as a time-limited concession to a private entity.

But all this seems a long way from the “official classification” in the title of the post, which I take to mean a public-facing classification that shapes the way regular users see the road network. I just don’t think the “admin level of the maintainer” is generally useful for that purpose.

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I agree entirely. However this was in the OP:

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We already have this tagging. In the United States, this would be network=US:I and network=US:US. The use of network=<country_code>:<network> is pretty close to a global standard with the exception of a small number of countries.

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This doesn’t make any sense. How are you going to “fix incoherence because of borders”, which is to say you’re somehow going to harmonize the tagging of roads across international borders, by introducing a “national, official classification” tagging scheme which by definition will lead to these sorts of incongruities because countries classify their roads differently? In your linked example, if France classifies that road D981 with less importance than Belgium classifies N85, how does that do anything but cement the status quo, which you’ve decided is “incoherent”?

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Is this more angst arising from Poland’s dual systems of road classes (pertaining to design parameters) and road categories (for wayfinding)? Some other jurisdictions have analogues to Polish road classes that are tagged in very obscure keys, befitting their very obscure nature. Unifying them all under a common system seems counterproductive, like papering over the chaos that exists in the real world. But if you want, you could stick this information in our common junk drawer, affectionately known as designation=*, to make it less likely to be consumed by software.

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Exactly.

[filler for the character limit]

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Sounds reasonable. One thing I’m wondering is if there could be a possibility of a global tag to make an international map based solely on official classification but that’s probably impossible because of the diversity of classification systems.

What about E-networks? Maybe something like network=EU:E;…?

After the information about official classification gets moved to a new tag, the highway=* key can be used to achieve coherence instead of these things you see. This road serves a connection between two towns with population around 5k so it definitely doesn’t deserve highway=primary. A road doesn’t randomly change its importance when it crosses a border.

Poland already has tags for it so that’s not an issue. I’m just trying to introduce it in other countries which just can’t be convinced to change their strict connection between highway=* and official classification even when it’s hurting data consumers. If most countries don’t have this second classification, that only makes the job easier.

Do they follow the typical meaning i.e. something related to road parameters?

If you have to type filler for the character limit, that clearly shows that you’re not bringing anything positive to the discussion. Seriously, nobody is forcing you to engage in these.

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International networks are non-prefixed. For example, E-roads are tagged network=e-road.

Not only are these tagged, but they are also used in maps.

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The E-road network is designated by UNECE, not the European Union. It’s an entirely different body that even includes Canada and the U.S. for some reason.

Various UN commissions and congresses have designated similar networks all over the world. The E-road network overlaps somewhat with another UN-designated network, the Asian Highway. Most of these networks already have well-established network=* values without namespacing, with the exception of the Central American Highway Network (which overlaps with the Pan-American Highway).

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I dont think thats a viable goal.

The classification of roads does not and should not be the same in every country. Road classifications dont have an “absolute value” or “priority” per se.

Road classifications reflect the administrative importance within the regional road network. Its not even the importance by usage. Its the importance by administrative planning.

This is why OSM by definition made road classifications by defacto usage/importance and not by administrative classification.

So by adhering/linking the OSM classification to some administrative planning classification we loose having a road network as its beeing used on the ground, and replaced it by some “Parrot” talking through the administrative bullet points.

In a lot of countries these classifications are pretty close, but its not everywhere.

Flo

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There is just too much variation between different countries’ systems for this to make sense. The UK might have a coherent system that allows for a one-to-one relation between official highway classification and OSM, but this is not true in all places. Each country’s mappers should consider whether to base their classifications on the official ones, but ultimately we should try to keep the meaning of each highway=* value relatively consistent across countries. Following the UK’s system which we got our highway=* system from, this means highway=motorway and highway=trunk are of national/international importance, with highway=primary and down of descending importance.

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To me a road between two towns of 5,000 people apiece could easily be of “primary" importance. And I’d hardly call crossing a border a “random change”. If the road is more important to the Belgians than the French who are you or I to tell them otherwise?

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The official schemes I’m familiar with are based on a variety of things. Some of them are based on technical design parameters. The tags for these schemes are not only obscurely named: the very idea of mapping them is very obscure. Despite our love of high-vis jackets, most mappers are not professional surveyors or project managers on road construction crews.

I’ve always been surprised at how much the Polish public seems to know about the Polish system of road classes. In the U.S., we have the Interstate Highway standards at the national level and equivalent design standards at the state and local levels. The number of people in my state who are familiar with these standards is probably in the low hundreds, most of them government employees. A given highway’s conformance to these standards has probably come up at some point in a meeting minute or other official correspondence. But what if the documents are unavailable to the public or too restrictively licensed?

A mapper could probably tell that a stretch of highway is very substandard based on things we already have tags for, such as vertical clearance (maxheight=*) and lane width. But we lack the ability to evaluate a less clear case based on the highway’s design speed, design hour volume, cross slope, or marking reflectivity, as required by these standards. No one is going to stop traffic on a busy highway and measure the cross slope with a DIY level just to be able to classify the highway. Then again, reevaluating a highway for conformance to these standards would totally miss the point of the standards, which are for planners and decisionmakers.

Alongside the technical standards, there’s functional classification (HFCS=*) and strategic classification (NHS=*, Texas_Trunk_System=*), all tied to funding. These keys only really exist to console mappers who fret about our map potentially showing different colors in different places than a PDF map on a .gov site. Some states have similar schemes that are implied by route numbering schemes, so we don’t bother to tag them at all. There are special classification schemes for truckers that are tied to access restrictions (hgv:national_network=*, hgv:state_network=*), good for truck routing only. More importantly, there are less technical terms like stroad and expressway that are defined more holistically – based on vibes, even. These terms are actually useful because no one can define them perfectly.

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that’s interesting, I wasn’t aware of it, this way you can even have different formalized values to mean the same thing in the same country, but in different languages.

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This statement is confusing, because on the face of it, it suggests you want it to correspond to the official classification, but actually you don’t. You want to move that info into other tags.

As mentioned above, there is operator=* that you can use.

This problem only arises because you want to include the operator within the classification. It makes more sense to separate them entirely. If a community decides that’s too much duplication, then they can omit either if they want, but that’s for the local level to decide.

They refer to the design standard that the road was built to. This usually correlates with importance, but can diverge over time if demand patterns change.
This could be tagged with highway:category, though something like design_standard:<name of design manual used for planning>=<design standard> might be more universally applicable. E.g. Germany has three different manuals depending on the official classification (RASt, RAL, RAA) and even just for motorways and motorroads (RAA), there are three different classes (Entwurfsklasse 1, 2, 3) before they are classified by road width (e.g. RQ 43,5[1]). Food for thought.

Edit:

Just found in the RASt 06[2] the common design situations [3] that it’s used for. This is the closest thing to an official classification as it’s based on (planned) usage patterns and (expected) traffic volume. I’ll leave them here untranslated and for most, there are several design standards possible:

Wohnweg
Wohnstraße
Sammelstraße
Quartiersstraße
Dörfliche Hauptstraße
Örtliche Einfahrtsstraße
Örtliche Geschäftsstraße
Hauptgeschäftsstraße
Gewerbestraße
Industriestraße
Verbindungsstraße
Anbaufreie Straße

This list is basically what you want to put into OSM tags. Most of these would fall under highway=residential or highway=unclassified and usually don’t have an official designation (Bundesstraße, Land-/Staatsstraße, Kreis-/Gemeindestraße).

  1. width in meters, RQ=Regelquerschnitt (standard cross-section) ↩︎

  2. Design manual for city streets ↩︎

  3. on page 11 and 12 ↩︎

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