gmar5, Nathan_A_RF and I have had a dispute over the tagging of the A420 in central Oxford. At present, the A420 is tagged as highway=tertiary contrary to the OSM Wiki page Roads in the United Kingdom, which stipulates that there exists a wider consensus for roads to be tagged by their legal classification, i.e. the colour of their signage on the ground. The wider consensus for secondary A roads (e.g. the A420) is that they should be tagged as highway=primary. gmar5 argues that the A420 is functionally identical to a tertiary road and therefore should be classified as such. Conversely, Nathan_A_RF and I argue that the guidance on the OSM Wiki page should to applied evenly across the UK to avoid confusing users of the map. I have initiated this discussion here to in the hope that the wider OSM community will provide input to resolve the dispute. Prior discussion can be found at changeset 119965203. I will notify talk-GB of the discussion too.
The note is saying: this road is officially designated as primary, but it is de facto a tertiary road.
So… which holds more weight, the de facto status or the de jure status? De jure for me. There are plenty of classified roads in the UK (ie ones with actual numbers) that have sections, typically in town centres, which are heavily restricted in terms of which classes of vehicle are permitted to use them. However until they are formally declassified (to discourage use) they still have that classification and should be mapped as such. Other tags on the highway, eg bus=yes, motor_vehicle=destination, should mean that drivers aren’t routed that way, whatever the designation of the road is.
(An example of formal downgrading would be the B6546, north of Sheffield, which was the A629 and indeed breaks the latter route in two.)
The “only map what’s on the ground” ethos is a very good guideline, but sometimes signage is missing (sometimes for traffic management reasons) or just plain wrong. The mapper should exercise their own judgement in these situations and I would argue that the intended meaning should be mapped. If you know better, impart that knowledge.
Like your example, this is a restricted traffic zone (buses, taxis and local traffic for the station only) and there is even a bus gate.
In this case, the restricted part of the road is tagged as highway=unclassified and the bus gate is tagged as highway=service. Yet both should be highway=secondary if we go off the legal designation (a B road) and the UK tagging guidelines.
Yes the high street in Oxford is very much a special case and technically violates our normal tagging rules - this was discussed to death years ago on the talk list and the current solution was agreed on.
Here an old mention by @Richard from way back in 2009:
Please let’s not relitigate this. As @TomH says, Oxford High Street has been treated as an exception to the rule since the very first days of OSM - here’s a 2007 link! - since you can’t actually drive down it for most of the day.
It would really help if people would do a bit of googling before opening up things that are long settled… this just wastes everyone’s time.
One simple question to the advocates of tertiary: Is this part of a campaign to declassify the road? If so this is mapping “ought to be” instead of “is”, which OSM shouldn’t accept.
Seeing good arguments in favour of the local consensus; it could go either way, honestly. I think it would be better if everything is kept consistent per the guideline, but I’m content with how things are going. Would it be worthwhile to add a tag to the A420 to check the recently added note about the A420 on the OSM Wiki to stop relitigation of the dispute?
To be fair, I destroyed that beer batch a couple of years ago.
To clarify, maybe adding the link to the OSM Wiki page about the newly added section regarding the A420 on OSM could be useful at stopping further relitigation like this in the near future?
Sillyposts aside though, I’m in favour of keeping it mapped the way it is, as a tertiary road. It’s what’s actually there, innit.
To be honest, if other towns and cities with mediaeval cores have A-roads lined through their middle, but heavily constrained through traffic on them for all the usual reasons*, then OSMUK should break with de jure tagging that and go with de facto instead. Make it visually close to reality, so it’s right for route selection by humans.
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* narrow layout, external bypasses, or newer things like ZEZs, pedestrianisation, or camera enforced bus gates
Sorry but I feel you can’t just rewrite the wiki to fit your position. There are lots of other roads with a classified status that have access restrictions of some sorts in one or both directions, and yet these are all still marked as per the wiki guidelines. Access restrictions do not dictate the status of a road.
If the A420 here should be tertiary, then what’s to stop more subjective changes to other roads based purely on traffic numbers? Tertiary roads upgraded to primary as they have four lanes? Secondary roads downgraded to unclassified because they are basically country lanes?
Both the A420 and the B4100 should be tagged as their respective status regardless of any access restrictions.
The oldest explanation I can find on the wiki of why Oxford High Street is nothighway=primary dates from 2007. If there’s any “rewriting” going on, it’s from the “A road so must be highway=primary” faction.
The codes for tagging roads in the UK is longstanding, that hasn’t been rewritten, just written originally! And just because something was discussed in 2007, it doesn’t mean it stands forever.
This point should be emphasised; consensus can change. Discussion is integral to evaluating the established consensus and this goes both ways. Personally, the OSM Wiki is the best (i.e. most accessible and readable) place to note exceptions to longstanding guidelines like the A420 and B4100.
If any changes were to be made, the A420 could perhaps be tagged with access=no in conjunction with highway=primary. For example, to the west of the A420, there’s a tertiary road tagged as access=no (Norfolk Street). This would reflect the situation on ground (access=no) while reflecting the legal status of the road (highway=primary).
I’ve changed the note to link to the OSM wiki page. CS156363823
I was just going to complain about another example of “guidelines” ignoring the objective reality and trying to shoehorn official road classification into the sometimes unreconcilable OSM tagging - only to see somebody added common sense to that wiki page already.
If data consumers wanted legal status for a road, there are (I assume?) other datasets, including those provided by the government, that show the planners’ views and dreams. If a motorway carries tertiary-level traffic 99% of the time, it is realistically matching the highway=tertiary definition, regardless of what The Documents might say
Except that the legal classification indicates the importance of routes and does not reflect the level of traffic at all. Do you wish to mark the majority of roads in the Orkneys and Shetlands as tertiary roads? That would make the map objectively worse, just as opening up a subjective classification can of worms would by increasingly dismissing guidance and being more flexible.
Indeed, access tags on a way should not dictate its status and are a calculation part of the routing engines, with routes following high classification roads and routing around such restrictions - which will be the case here whatever status the A420 (or B4100) has.
Could you clarify what you mean by unreconcilable tagging, please? I don’t think I understand what you’re saying here. Are you suggesting that current guidance on the tagging of roads in the UK is flawed in some way?
The “planners’ views and dreams” are what’s on the ground. The A420 is an A road with restrictions disallowing motorists from the general public using it; that’s what the planners intended. Why do you speak of them negatively? Wynndale said it well — we shouldn’t map things how they’re “ought to be”. Instead, we should map them how they are.
A motorway isn’t even remotely comparable to a tertiary road on the ground and in legal documentation. This is an absurd interpretation of the well-rounded and longstanding guidance that we should map what’s on the ground. Nathan put it right; roads are generally classified on the importance of their route, not the level of traffic they carry.
