The meaning of "Change highway tags to reflect real usage"

Communities Oceania
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In South Australia, Over the last week a number of roads have been edited to change the classification from the actual usage of the road according to Data SA. The changesets Changeset: 146810025 | OpenStreetMap are left with a comment of “Change highway tags to reflect real usage”. I would like to point out Gawler Street, Salisbury.

Gawler Street never used to be a Secondary road barely could even class it as a territory road either!. Sailisbury Interchange is a major public transport hub cater to roughly 10,000 people per weekday and fluctuate depending on events in Adelaide city on weekends. October 2002 4 school kids were riding in a bus on their way home from school, the route the bus was taking turned right on to park terrace from salisbury highway. Due to congestion the bus became stopped over the railway line with nowhere to go. The Ghan which is a huge luxury passenger train was north bound heading towards the park terrace railway crossing. It couldn’t stop in time and crashed into the school bus. 4 kids lost their lives in that accident. it lead to a major overhaul of way the interchange operated. If you look at the bus route relations in OSM today you can see that no buses go over the railway line anymore… infact they don’t go through that section of park terrace at all. its not just buses its also trucks and long trailers. Gawler Street became the link to the primary network of salisbury highway. The city of salisbury built a memorial in the honour of the victims. Gawler Street needs to keep the secondary classification to divert traffic the intended and safest route to the primary road network. It is up to us to do whatever we can to prevent a disaster like this happening again.

The “real usage” is a secondary road, but more importantly secondary is the actual nature of the road. After my blocks winds up if a discussion here decides otherwise I intend to change this road back to secondary to reflect the actual usage of the road.

Thankyou

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Whilst I’m not a local, how it is currently mapped (Park Terrace as secondary, Gawler as tertiary) looks right to me. Changing this and putting blind faith in government data would be wrong in my opinion.

I think you should also remember that routing apps that utilise real traffic data probably don’t pay much attention to the road classification as they have enough traffic data to know how best to route vehicles.

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If you want to better understand real usage, spend some time in the area observing traffic flows or asking local drivers about the routes they take.

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I believe that sentence is the wrong way around, we should use the official classifications unless somebody does a real world survey to prove otherwise, I am a local and I believe that gawler street should be secondary.

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The thing is, it has become hard for me to believe that you genuinely believe that is correct as you have clearly (from your other posts) become obsessed by the government dataset.

I gather you have a block on your account at the moment. If I were you I would take a break from road classifications. Go map something else instead for a while.

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this is actually the perfect time to discuss to be honest. The wiki has a strict definition on what constitutes the classification of a road. For starters I am just asking what “real world usage” means and how it relates to the OSM wiki and guidelines. What you have said in your first reply can easily be turned around to these edits, putting blind faith in anyone who feels the need to change the class of a road with “reflect real world usage” as the changeset comment. The wiki says that the “actual nature of the road” which is defined by the official (government) classification. Real world usage seems made up which is why I am just asking for clarification on what they exactly mean.

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and again am just asking so there can be some kind as recorded definition and if it is acceptable within the OSM wiki. Do you have a issue with this?

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As slice0 has specifically asked me to contribute here, I’m going to post a wiki link that I have previously posted in regards to this general topic, and that describes how anything in OpenStreetMap should be primarily mapped.

https://wiki.openstreetmap.org/wiki/Ground_truth

We should map highway classifications based on what we can see, looking at a variety of things including how heavily a road is used, the design of roads, whether traffic calming devices exist and how easily traffic can flow.

A great example of this is, as mentioned, Park Terrace and Gawler Street in Salisbury, South Australia. One is a 60km/h road with 2 lanes on each side with traffic lights at all main intersections along it, and right of way where any other road intersects with it… The other is a 50km/h road with 1 lane on each side, all intersections with other roads are uncontrolled (two roundabouts at most) or are where the road starts and ends, and has segments of streetside parallel parking on it.
Looking at these two streets, one clearly is aimed to have more traffic flowing through it and the other is aimed to provide access to destination streets. All of this is from looking at aerial imagery we have access to use for mapping purposes in OSM.

To talk on the point about diverting traffic, we aren’t mapping for routers or renderers, we map what’s there. It’s as simple as that.

This is how OSM is mapped, we focus on what’s on the ground, and use official data to help supplement that. We take road names from sources where possible because it’s easier than trying to check every street sign, but if a street sign said otherwise, we’d use that instead. OSM’s biggest advantage is the community, and that we’re all over the world and can verify what’s in the map compared to what you’d see at that exact same location.

I’ve said most of these points to slice0 several times throughout this saga, as have many others, including the DWG and members of the OSMF board.

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A view from the other side of the world:
The importance and classification of a road is based on the number of vehicles rather than the number of people using the road.
When I look at various street view pictures, I see 2 lanes and few vehicles including buses on Gawler Street. In contrast, Park Terrace has 4 or more lanes and many more vehicles (but of course no buses).
From a distance, it seems ok that Park Terrace gets a higher road classification than Gawler Street.

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if I can also clarify, when I was firstly looking into the information from Data SA I was lining it up one classification at a time rather than a whole. Tag:highway=secondary - OpenStreetMap Wiki The line being “highways which are not part of major routes, but nevertheless form a link in the national route network.” and “Secondary highways are generally specified by country road classification bylaws” together do match up with gawler street street being class as secondary, especially because gawler street handle thousands of bus and train commuters everyday. The one way road john street and the big shopping center have entrances from gawler street, there are government entities and doctors offices along gawler street as well, which adds to the traffic load. This was my reasoning for siding with the official data. I think both reasons are valid to be honest and I would like to find a middle ground somewhere, someone has mentioned to me that there is a another tag we can use that separates the “render” classification from the official. I think it would be good to still have the official data included. I accept your position on Gawler Street being as it currently is and would like to move forward. The major traffic route does not have to be trunk either, the roads can be changed to what they are “classed as” or “real usage” and the major traffic route can be tagged similar to route numbers so we dont lose that information either.

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Not at all. And it seems like the replies to the thread below go a long way to answering this for you. I would just add that lots of frontages (shops, government entities and doctors) does not increase the classification of the road. In fact it likely decreases the classification. Consider motorways for example; they have no shops directly on them. Residential roads are full of active frontages (i.e. people’s homes and their driveways).

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I mentioned the buildings because they add to the traffic flow, there is a cinema on gawler street as well, just trying to say that it is far from a quiet little street that you see by looking at imagery. I took the amount of traffic in consideration when weighing up the government classification at the time.

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as fortura mentioned “heavily a road is used” is a criteria for the “real world usage” definition, I can assure you that it is very heavily used

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Hello!

What strikes me: There is a rule about access (although for truck it would be better to set hgv) and also all relations go the “right” way. That’s what routers need, isn’t it? So why is it so important to downgrade the OTG larger road? :thinking:

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However Park Terrace is definitely used much more than Gawler Street.

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if you have a look at the entrance to the bus terminal Way: 103971749 | OpenStreetMap there are currently 9 bus route that enter via gawler street, granted I have not look into how often these bus’s do their routes. This shows a very significant number of buses alone. the OSM Wiki definition of a Urban Tertiary road is as follow " Within larger urban settlements such as large towns or cities, tertiary roads link local centres of activity such as shops, schools, or suburbs. Use only for roads with low to moderate traffic. For the quietest sort of linking, non-residential road consider using highway=unclassified instead. For busier through routes and main roads use highway=secondary or greater." So I would just like to point out that Gawler Street may fall under the " For busier through routes and main roads use highway=secondary or greater." sentence as it is a very busy through route. However as I have said before I dont disagree with your classing it as Tertiary however there is a chance it may fall under the “busy through route” category.

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I have to ask then, why did you originally change it from tertiary to secondary: Changeset: 141376507 | OpenStreetMap, then continue to fight over it since: OSM Deep History

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because its fits the definition of Secondary by every single meaning as described here Tag:highway=trunk - OpenStreetMap Wiki and here Tag:highway=secondary - OpenStreetMap Wiki and it also being the “actual nature of the road” Australian Tagging Guidelines/Roads - OpenStreetMap Wiki , I dont disagree with it being classed as tertiary based on if there was no government data I would probably lean towards tertiary as well based on my own personal “ground knowledge”

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very interesting discussion when you look at this from the other side of the world.

Normally, local mappers should agree on which classification a road should be given. It seems to me that this is not possible in your case. Hence my view from very far away …

What is the source of your figures?
How many of them travel by bus, bike or car? How many walk?
But I already wrote that the number of passengers doesn’t really matter. At least 10 times more passengers fit on a bus than in a car. Sure, a large proportion of passengers use the car. If I have seen it correctly, there are three large P+R car parks: two to the west site of the railway line and only one to the east, accessible via Gawler Street.

This ist a wish - and the other side is the real usage.

Wiki says:

Note that highway=* distinguishes roads by function and importance rather by their physical characteristic and legal classification. Usually these things are highly correlated, but OSM is not obligated to copy official road classifications.

In my opinion, four points should be assessed:

  • physical characteristics
  • importance
  • function
  • official classification

Physical characteristics:
In my eyes, Gawler Street looks like a typical unclassified in urban area with shops and a cinema. I see narrow lanes, pedestrian crossings (zebra) and some cycle lanes. This rather speaks in favour of a lower classification like unclassified.
It has already been upgraded to tertiary, which I think is right. Because:

The importance:
Gawler Street is an important collector street and serves as a feeder road to the shops/shopping centre, cinema and railway station. (see here)

Function:
It seems to me that Gawler Street connects the shopping centre and the railway station (a local area) to the road network, but it is not a major thoroughfare connecting neighbourhoods.

Official classification (is just one point among several):
Park Terrace is a road that is maintained by Department for Infrastucture and Transport (SA) - and I think SA means South Australia and not Salisbury :wink:
Gawler Street is maintained by the City of Salisbury.

Considering all four points and in comparison to the road network as a whole, I think the classification as tertiary is correct.

whats the source? The LocationSAMapViewer hat I found?
Is this a valid source?
There is no roundabout on Gawler Street.
image

And this dead end Winzor Place is a secondary?
image

Do you understand why I doubt that Gawler Street is correctly classified there? Official data doesn’t always have to be correct.

Or: I believe that this MapViewer does not visually distinguish between tertiary and secondary, as OSM does.

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My last reply to fizzie I have said that I agree that it is a tertiary road.