Visual characteristics of 'unclassified roads' as you understand them

General talk
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Please understand that I am posting this here once again to share with various regional communities and contributors. Your broad range of opinions is needed.

There appears to be considerable confusion about ‘unclassified roads’, which originated from the UK road system, and there seems to be a lack of consistency in tag application within OSM as well.
Therefore, I’m writing this post with the hope of clarifying the concept of ‘unclassified roads’ for regions outside the UK and Europe, and providing reference material when considering the use of the ‘unclassified road’ key in those areas.
Since road system definitions and legal classifications from the UK may not be applicable elsewhere, I’d like to set aside legal or administrative aspects for now and focus solely on a few visible, outward characteristics that might help identify such roads in mapping practice.
I would like to hear opinions not only on how the ‘unclassified road’ key is understood and used in other regions, but particularly from contributors in the UK and European regions.

Unfortunately, I haven’t had the opportunity to visit the UK directly, but I have encountered roads in various parts of Europe that I believe might correspond to what OpenStreetMap refers to as ‘unclassified roads’. Based on that experience, and after reading several documents available online, I’d like to summarize the physical characteristics of ‘unclassified roads’ as I understand them.
I would be very grateful if you could let me know whether the following points are reasonably accurate as physical characteristics of ‘unclassified roads’, or if I’ve misunderstood anything. Additionally, if there are any visual or structural features that I may have overlooked, I would sincerely appreciate your guidance.

  • They are generally surfaced with asphalt concrete. Since this road surfacing material cannot typically be used freely by anyone due to legal restrictions, I understand its use as evidence that public administrative power was exercised.
  • They usually have no road markings, or in some cases, only a simple centreline (often a white solid line) for convenience. Edge lines are typically absent. (Some may have no markings at all.)
  • There is usually little in the way of road signage, particularly for traffic control or guidance. However, basic signs may exist at junctions or along longer stretches of road to assist with navigation.
  • There may be farmland or grassland alongside the road, but accessing the farmland or grassland is not the main purpose.

The above points are the general criteria I currently use to identify ‘unclassified roads’.
Do you think this description reflects the typical characteristics of such roads in Europe, where road networks developed early? And are there any other visual indicators or features you would recommend looking out for when tagging ‘unclassified roads’?

I’ve added some notes below to explain why I’m focusing on the physical characteristics of “unclassified roads.” Please take a look!

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As a mapper based in southern Ontario, Canada, my understanding of unclassified roads is that they are roads that are less meaningful than tertiary but not service roads, and largely don’t have houses on them.

I don’t associate them with visual characteristics because those vary very widely. It could be a street in a city in an industrial or commercial area: paved, curbs, sidewalks, traffic signals. It could be a road in the countryside that looks like the one you posted. It could be an unpaved road through a forest.

Some examples if you want to try extracting common visual features:

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First of all, I understand that British mappers no longer strictly apply highway=unclassified to what the authorities call “unclassified roads” and occasionally mark with an erroneous “U” road number sign. It’s technically a misnomer along with highway=trunk (not necessarily the designated trunk roads) and highway=primary (not necessarily the green primary routes). Instead, the documented definitions basically distinguish highway=unclassified from highway=residential solely based on abutters=*.

Across the pond, the U.S. mapping community has grappled for years with highway=unclassified. At first, when there was a strong desire to map highway=* values one-for-one to route networks, mappers in some states established a baseline applying unclassified to the roads maintained by admin_level=7 governments, while mappers in other states avoided the tag altogether because there is no government at that level.

For example, in the Midwest, tertiary was generally used for county roads, unclassified for township roads, and residential for municipal roads, regardless of abutters. Depending on the area, township roads could be well-constructed urban roads, rural dirt paths, or anything in between. For completeness, here are the exemplar images in a visual field guide for Ohio largely written during this era:

It was a very regional approach, but we saw the classification tags as nothing more than a scale to fit our own local needs into. These days, we’ve grown out of this heuristic. For consistency with the rest of the world, nowadays, we generally apply highway=unclassified to local streets without residential abutters. But it sure feels like an arbitrary distinction better captured as abutters=* or landuse areas. For this reason, there have been occasional musings about abolishing highway=unclassified to simplify the classification system.

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I believe we can all agree that road classification systems vary greatly from country to country.
When we take each country’s local context into account, it can even seem more reasonable to create separate classification systems for each country, no matter how much we try to simplify things.
That said, it isn’t really feasible to apply completely different road classification systems for every country. Instead, we need to do our best to align with the existing structure of OSM.

In any case, it’s clear that the term “unclassified road” has led to various misunderstandings and confusion.
(And for contributors in regions where the concept of “unclassified road” is well understood and consistently used, I think it’s important to acknowledge that this is not the case everywhere.)
In that sense, as @Minh_Nguyen mentioned, if a tag causes ongoing confusion and misunderstanding, I think it could be worth considering deprecating it.
However, I don’t intend to broaden the scope of this thread to that level of discussion.
(Once the discussion reaches a deeper level, I believe we may be able to find better alternatives or directions.)

That said, I do believe it’s important to identify and clarify some consistent attributes of “unclassified roads,” so we can reduce confusion and improve tagging across different regions.

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Sure, but in line with what @Jarek said, we can’t rely too heavily on visual characteristics for that. Your example photo could easily be a tertiary road, there is no way to tell without knowing where it comnects to. I see there is a direction sign at the far right but I can’t read it.

Generally I don’t see many roads connecting villages tagged as unclassified - they would typically be tertiary. I often see the unclassified tag applied to roads used to reach some non residiential amenity or point of interest: a recycling centre, hotel, industrial zone, or nature reserve with visitor facilities. They may be compacted rather than paved. They are more likely to be “dead ends” than tertiary roads (you reach the point of interest and have to tun back), but that’s not a hard-and-fast rule.

Coming back to your photo, if the direction sign points to the name of a populated settlement I’d say it is more likely to be tertiary. If it says, say, “recycling centre” It might be unclassified.

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In the UK, insofar as there’s any relation to the road classification system, all highway=unclassifieds are “unclassified roads”, but not all unclassified roads are highway=unclassified.

The mapping is:

  • highway=motorway: motorway
  • highway=trunk: green-signed A road
  • highway=primary: black/white-signed A road
  • highway=secondary: B road
  • highway=tertiary or unclassified or residential: other public roads without M/A/B number, aka “unclassified road”

(The existence of “U” or “C” or “D” or “E” numbers - or anything else - is an administrative detail for highway authorities, not public-facing, and not interesting to OSM, though some completists do record them.)

All would be expected to be paved - we have very few unpaved public roads in England & Wales. In the rare case of an unpaved public road we’d add a surface tag.

Generally the divide between the unclassified road types is:

  • highway=tertiary: significant through traffic between settlements with engineering features to match (typically centreline, two vehicles can pass, etc.)
  • highway=unclassified: less significant through traffic
  • highway=residential: road within settlements principally for access to housing on this or adjacent roads

In the UK, it’s usually fairly obvious in practice - centrelines in rural areas are a big giveaway - although a few mappers do go overboard on highway=tertiary. Typically I would expect more unclassifieds in an area than tertiarys, though in (say) commuter belt Buckinghamshire you’ll find more tertiaries and in rural mid-Wales you’ll find more unclassifieds.

Broadening it out to internationally, I would say the above broad principles (without the specifics about centrelines etc.) are good for developed countries. I’ve just spent a fortnight cycling through rural France and the situation is not that different from the UK; French mappers would perhaps use highway=tertiary on an edge case where we’d use highway=unclassified but there’s not much in it.

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What would be helpful would be to link to other, similar, posts that you’ve already made. Lots of people have experience of how OSM tagging maps on to physical characteristics and legal classification in several regions, and trying to “manage replies” like this is a bit confusing.

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Whilst most public roads in England and Wales are either asphalt or concrete there are absolutely no legal restrictions on the use of these materials on a private road.
The surface or lack of it cannot be used as evidence of public or private ownership or access.

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In hilly areas of Balkan countryside, houses are often scattered in isolation or in small clusters (that I dare not call “hamlets”) among forests, meadows or small orchards and farmland. The connecting roads are single-lane, either compacted or paved; however, because of such layout, they lack a clear classification between residential and unclassified. See this one, as a typical example (switch to Edit mode to get a better idea about surroundings, the map is not very detailed):

Now, it’s not a problem in itself, since residential and unclassified are generally treated the same by routers and renderers, and we just go by mappers’ “gut feeling” – in this case, I judged that a dozen houses over a stretch of 2 km does not make a residential. Just sayin’ that there are roads do escape a clear classification.

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I am old enough to have driven in France when the road system was far more like the UK than it is today.

Trunk roads could very much be considered in the same way as Le Route Nationale with two lane

I am old enough to have driven in France when the road system was far more like the UK than it is today.

Trunk roads could very much be considered in the same way as Le Route Nationale with two lane roads alternating between 90kph NSL in rural sections and 60kph urban sections as they passed thout villages and towns. In my 20s I avoided the expensive autoroutes.

I fondly remember RN1 from Calais to Paris, passing through the village of Nouvion (David Croft must have also travelled this road).

In the 90s France departmentalised their road system and the former Route Natioanle mostly became D roads making the historic routes harder to find and making it more difficult to follow the fun routes and ensuring satnavs direct you onto the toll autoroutes.

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Here in Germany, the road classifications roughly match with the UK system, though the primary distinction is which government owns a road: A road owned by the federal republic (Bundesstraße), a road owned by a state (Landesstraße), a road owned by a county (Kreisstraße) and lastly, every other road (owned by municipality, place, landlord, etc.). The system roughly matches with highway=primary, highway=secondary, highway=tertiary and highway=unclassified/residential/service/etc to the importance of the road in relevance of Germany itself and the various regions (e.g. the federal state takes a particular interest of maintaining roads of national interest while the individual states particularly maintain these of statewide interest) (highway=trunk is a special case in which the distinction is strictly by structure i.e. grade separated and no overtaking allowed regardless who owns the road but this isn’t a universal practice and highway=motorway also have to be legally classified as this alongside being dual carriageways instead of just a single carriageway with no overtaking permitted).
That being said, there are plenty of exceptions for various reasons such as how the ownership of a better built bypass of a settlement may not have been transferred while the settlement’s main road is still part of a federal or state highway despite the fact that driving there through is impractical especially with a large vehicle like a lorry. Conversely, a lot of Kreisstraßen (but not Bundes- and Landesstraßen) lead to a dead end because they’re the main road to an otherwise isolated settlement and such highways would only have a classification as major as highway=unclassified in part because you can’t continue a highway=tertiary and also because such a road is strictly for local traffic only.

From my German POV, a highway=unclassified is any road under one (or more) definition:

  • The highway leads to a dead end (at least for cars) but is exurban (few to no driveways). The road will be highway=unclassified until the next junction.
  • The settlement is minor and there aren’t any reason to take this road as a shortcut, regulations or otherwise (furthermore, such road will still be highway=unclassified inside the settlement akin to the “no broken up classifications” of higher classification instead of highway=residential).
  • More rarely (and essentially an extension of the above), it can be used to tell that it’s the main trunk of the settlement’s traffic (essentially a very local highway) while the others lead to a dead end (making them highway=residential).

In additon, highway=unclassified is also commonly used for local roads in an industrial area in Germany under the idea that such roads are non-residential because few people (if any) live there and the primary targets are the factories and businesses, though this isn’t a quite universal practice.[1]

  1. Relevant discussion: Klassifizierung von Straßen in Industrie- und Gewerbegebieten - #11 by Mammi71 ↩︎

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visual

but highway=tertiary / highway=trunk / highway=unclassified etc is about role of road in network, not about its visual characteristics

highway=tertiary may be unpaved and highway=track may be paved

this will be likely highly misleading

see first reply in A question regarding the visual characteristics of unclassified roads starting from

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‘unclassified’ is perhaps best defined by what it is not. It’s not important enough to be tertiary and it doesn’t fit as service, track or residential. In rural western US they are usually unpaved.

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In Northern Ireland, the legal technicalities are slightly different from other parts of the UK.
(Pretty much all of the land that the roads run over is privately owned - even an ordinary person like me technically ‘owns’ my half of the road that runs past my house :upside_down_face: - however a ‘common law’ right of way exists, which means the public have a right to pass along the road… meanwhile, since 1973, these roads have all been ‘adopted’ by an agency of a government department, called the ‘Roads Service’.)

The Roads Service classify all their adopted roads in to either

  • motorways (M)
  • trunk (A with green signs)
  • primary (A with white signs)
  • secondary (B) and
  • tertiary (C) roads
    …and all the rest are ‘unclassified’ (U)

The Roads Service give all of these roads a letter prefix and number.
Generally C and U numbers don’t appear on road signs, although very occasionally you will see a numbered C road of a sign (don’t ask me why!)
I prefer to reflect this practice by using the tag ‘highway_authority_ref=’ for C and U numbers that don’t appear on signs (rather than ‘ref=’). Arguably this is ‘tagging for the renderer’ but it does reflect a logical/practical difference in the use of the number.

All these adopted roads (apart from motorways) also have proper names, however these are assigned (and signed) by District Councils, not the Roads Service.

As to what the unclassified roads in Northern Ireland actually look like… well, it varies :wink:
They will all be at least 4 metres wide (enough for one motor vehicle to procede) although occasionally they may have bends or gradients which mean the Roads Service have to put an ‘Unsuitable for HGVs’ sign up. Most of them are wide enough for two vehicles to pass in either direction, but it’s usually a squeeze and you both have to slow down, or one of you wait at a ‘passing place’ (usually these are informal - eg at a gate leading into a field).
Pretty much all of them are paved with ‘tarmac’ (asphalt); commonly this is resurfaced every few years by ‘tar and loose chippings’. Many (probably most) of them don’t have any white line down the middle nor cats eyes, lines marking the edge of the road are rare. You will often see warning signs on them. Or ‘SLOW’ painted on the road (to be morbid, this usually means somebody died in a car crash at that spot some time in the last 50 years!). Some of them even have grass growing down the centre line! It is rare for them to have kerbs, pavements or street lights. Usually there is a grass verge or hedge (they are bordered by farmers’ fields). National speed limit usually applies except for portions that pass through a hamlet or villages.

To understand more of the context of these ‘unclassified’ roads: for at least a thousand years if not more, the smallest unit of administrative land division in Ireland has been the ‘townland’ (Townland - Wikipedia ). And almost all the land was farmland, divided up into fields. There were farm tracks designed for horse and cart, passing through and linking up all these townlands. During the early 20th century, a large portion of these got tarmac-ed and made usuable by motor vehicles. Prior to 1973 they were (inconsistently) maintained by a jumble of district and county councils, until finally in 1973 they were all ‘adopted’ by the Roads Service. So essentially nearly all of these little ‘unclassified’ roads are centuries old.

Everything I’ve said above primarily describes rural areas… in Northern Ireland’s urban areas, most of the residential roads are post-war (WW2). I would usually use the tag ‘residential’ for them, although the majority of them are still ‘adopted’ ‘unclassified’ U-roads maintained by the Roads Service. But they look different to rural unclassified road - they will usually have kerbs, pavements, street lights, 30mph speed limits, and enough space for two-way traffic - so I think the different tag makes sense.
(There is also a bit of a fuss in Northern Ireland about a backlog of new housing developments and their residential streets where the Roads Service has not ‘adopted’ the road, meaning nobody will pay to maintain it… so these roads are definitely residential, but NOT part of the Roads Service’s ‘unclassified’ category). Again note that in Northern Ireland, the legal or common law basis for the right of way on a road is a separate matter to whether it has been ‘adopted’ by the Roads Service - the latter is just about who pays to maintain it! So whilst in England or Wales, these unadopted residential roads might typically be called ‘private roads’, the issue with them in Northern Ireland is not a lack of legal right of way, it’s just an administrative balls up about who will pay to fix the pot holes )

There are also a large number of old farm tracks and lanes in Northern Ireland’s rural townlands which nobody ever got around to tarmac-ing in the early 20th century, so in 1973 the Roads Service never adopted them.
This left them in a bit of a limbo. Many of these are ‘dead ends’ that just provide access to a few farm houses or farms, but no through route. So in the absence of anyone else having any business to go down them, they tend to be de facto regarded as ‘private’ (so typically on OSM they get tagged as service roads, driveways, or track/land-access-road). These could often be hundreds of yards long, sometimes even a mile or two. However some were not dead ends, and provide through-tracks across townlands, connecting to (what are now termed) unclassified roads at either end. Historically, local people had enjoyed a common law right of way on many of these.
The help clear the limbo, in 1983 the ‘Access to the Countryside Order’ was brought in, which mandated District Councils to rediscover these limbo-ed tracks and ‘assert’ that a public right of way existed on them, and keep them open as public footpaths and bridleways. However in practice, local farmers are often having none of this. Nevertheless, the tags ‘designation=public_footpath’ etc are useful in that scenario.

Phew, I typed a lot there :upside_down_face:

I’ve no idea if any of that helps tagging outside of the UK or not!

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This should probably be a route relation with “unsigned_ref” for futureproofing. Using ref=* on ways to describe routes violates the “one feature, one OSM element” guideline.

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Blimey, does it? Pretty much every road in the UK I’ve ever seen on OSM just has a ‘ref’ (or ‘highway-authority_ref’) tag repeated on each segment of its way!

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To go back to the root of your original query: sadly I don’t there is is any unambiguous way to work out whether a road in Northern Ireland is ‘unclassified’ just by looking at it: tertiary (C) roads are often a bit wider than unclassified ones, and more likely to have road markings, but the difference is rarely clear enough that you could be sure. Many C roads look just the same as unclassified ones! And some unadopted lanes and driveways through farmland have been tarmaced and maintained to a high standard by the landowners, so could be mistaken for an unclassified road. (The lack of a street name sign could be a clue that a road in unadopted - but there are hundreds of unclassified roads whose name sign is missing, buried in a hedge, was knocked over by a tractor in 1985, etc)
Ultimately, it is administrative classifaction used by the Roads Service, and the only way to be sure is to look it up on their map (https://www.arcgis.com/home/item.html?id=e279a96616c94446906f9eb3c2923124 I think…)

This rather begs the question of how OSM editors knew which were which without copying it from Ordnance Survey or Roads Service data… but to counter that, when I look at the Roads Service map on OSNI, it is bloody full of my own OSM edits :joy: What’s going on?!? I guess they thought they were ‘open source’ :upside_down_face:

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No cause for alarm. As I understand it, a road number in the UK is considered to refer to a road proper, quite unlike in some other countries. The authorities also designate primary and non-primary routes but don’t give any of them a name or number, only indicating them with a green background behind whatever road number is posted. For some purposes, it might be tempting to model the numbered road as a relation, same as any street, but that’s another matter.

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I’ve been around OSM just barely long enough to remember OSM before relations existed as a primitive, when we only had ways and nodes. Routes and turn restrictions were the two main drivers for wanting both, because ref on ways was a bodge from before relations (and very annoying when more than one route is on a way, and even more annoying when routes are multiplexed for only part of their length). Plus it makes changing routes a lot harder when you have to retag a jillion ways to do it.

It’s been the better part of two decades now; the ref-on-ways-to-describe-routes dinosaur would have had time to be drilled out of the ground and refined into plastic and gasoline had we let it die when it should have.

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This is not the case. Randomly pulling up London, I landed on the A205 near the A23, which changes roads three times in as many blocks, traversing the entire length of Streatham Place on its way between Atkins Road and Christchurch Road.