Re: [talk-au] Unclassified Highway Speeds

[Graeme Fitzpatrick]

On Wed, 20 Apr 2022 at 15:02, stevea  wrote:

> At this point, I believe I am some Yank who babbles too much.
>

Not at all, AFAIK! :-)

 Thanks

Graeme
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Re: [talk-au] Unclassified Highway Speeds

[stevea]

Very nice to see this discussion.  At this point, I believe I am some Yank who 
babbles too much.
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Re: [talk-au] Unclassified Highway Speeds

[Dian Ågesson]

Hey Andrew,

I'm chiming in as I encountered this issue documenting the "cleaned up" 
Roads tagging guidelines. 
(https://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines/Roads)


The tagging guidelines (both prior to, and following cleanup) state it 
is good practice in Australia to tag every road with a maxspeed.


The early guidelines say that the implicit speed limits have not been 
widely adopted in Australia, but this no longer appears to be true.


In use is both the maxspeed:type tag and source:maxspeed tag. 
Unfortunately, the earlier guidelines offers advice on the usage of the 
source:maxspeed tag that is contradictory to the global page. (It 
suggests local_knowledge to mark implicit speed limits rather than 
AU:urban). The maxspeed:type tag does not have this contradiction.


I am not sure if leaving the maxspeed blank (or using a non-numeric 
value) would be a good idea; using a non numeric value in maxspeed seems 
to be much less preferred globally than the alternative methods. I 
documented maxspeed:type rather than source:maxspeed following a discord 
discussion, but I believe either of those two schemes are preferable to 
using maxspeed=AU:urban.


Dian

On 2022-04-20 13:45, Andrew Hughes wrote:


Hi All,

First, I thought the tagging guidelines were "don't tag unless it's a 
non-default value" (my language to describe this might be inaccurate, 
feel free to improve). If this is true, then I shouldn't tag rural ALL 
roads with  maxspeed. It's only those that are "non-default".


Can anyone please confirm the above please?

Secondly, it does look like there is a tagging for implicit (speed) 
values as per  
https://wiki.openstreetmap.org/wiki/Key:maxspeed#Implicit_maxspeed_values 
 [1]

maxspeed = AU:urban
maxspeed = AU:rural

I believe that the above is better than tagging 50kph, 60kph or 100kph 
- because a change in legislation (as has happened in the past) can 
change is without tags needing to be updated.


But that all being said, I would still be tagging all roads and not 
just those that are "non-default" on the ground. Which contradicts the 
first point (if it is true that is).


This feels like a distinct gap in OSM (as others have pointed out). But 
this is one I would like to know how to deal with.


Perhaps area's could be tagged with maxspeed=AU:urban or 
maxspeed=AU:rural  to define "implicit speed areas"? I think this might 
be what is missing. Thoughts?


Thanks for reading
AH

On Wed, 20 Apr 2022 at 10:30, Graeme Fitzpatrick 
 wrote:


In regard to defaults, the default 50kph Qld (Oz-wide?) urban 
residential limit should apply around here, & sure enough, most 
streets are 50. But we also have some residential streets posted as 
40, 60 & 70, as well as 40 conditional school zones.


So I assume (using that terrible word! :-)) that actually tagging a 
speed limit on a road overrides the default?


& while I've seen reference to Default Qld Residential speed limit on 
the map, I've also noticed while driving around that OSMAND isn't 
showing a speed limit?


Thanks

Graeme
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Links:
--
[1] 
https://wiki.openstreetmap.org/wiki/Key:maxspeed#Implicit_maxspeed_values___
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Re: [talk-au] Unclassified Highway Speeds

[Andrew Hughes]

Hi All,

First, I thought the tagging guidelines were "don't tag unless it's a
non-default value" (my language to describe this might be inaccurate, feel
free to improve). If this is true, then I shouldn't tag rural ALL
roads with  maxspeed. It's only those that are "non-default".

*Can anyone please confirm the above please?*

Secondly, it does look like there is a tagging for implicit (speed) values
as per
https://wiki.openstreetmap.org/wiki/Key:maxspeed#Implicit_maxspeed_values

maxspeed = AU:urban
maxspeed = AU:rural

I believe that the above is better than tagging 50kph, 60kph or 100kph -
because a change in legislation (as has happened in the past) can change is
without tags needing to be updated.

But that all being said, I would still be tagging all roads and not just
those that are "non-default" on the ground. *Which contradicts the first
point (if it is true that is).*

This feels like a distinct gap in OSM (as others have pointed out). But
this is one I would like to know how to deal with.

Perhaps area's could be tagged with maxspeed=AU:urban or maxspeed=AU:rural
to define "implicit speed areas"? I think this might be what is missing.
*Thoughts?*

Thanks for reading
AH




On Wed, 20 Apr 2022 at 10:30, Graeme Fitzpatrick 
wrote:

> In regard to defaults, the default 50kph Qld (Oz-wide?) urban residential
> limit should apply around here, & sure enough, most streets are 50. But we
> also have some residential streets posted as 40, 60 & 70, as well as 40
> conditional school zones.
>
> So I assume (using that terrible word! :-)) that actually tagging a speed
> limit on a road overrides the default?
>
> & while I've seen reference to Default Qld Residential speed limit on the
> map, I've also noticed while driving around that OSMAND isn't showing a
> speed limit?
>
> Thanks
>
> Graeme
>
>
>
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Re: [talk-au] Unclassified Highway Speeds

[Graeme Fitzpatrick]

In regard to defaults, the default 50kph Qld (Oz-wide?) urban residential
limit should apply around here, & sure enough, most streets are 50. But we
also have some residential streets posted as 40, 60 & 70, as well as 40
conditional school zones.

So I assume (using that terrible word! :-)) that actually tagging a speed
limit on a road overrides the default?

& while I've seen reference to Default Qld Residential speed limit on the
map, I've also noticed while driving around that OSMAND isn't showing a
speed limit?

Thanks

Graeme
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Re: [talk-au] Unclassified Highway Speeds

[stevea]

On Apr 19, 2022, at 4:29 AM, Andrew Harvey  wrote:
> ...Otherwise I think this will always be lacking in OSM until those maxspeed 
> tags are set.

Right: this is the crux of what I was getting at. Explicit data in OSM can be 
trusted, implicitly inferring data because of "defaults," well, not so much. 
(Or, it is highly ambiguous as you might attempt to do so).
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Re: [talk-au] Unclassified Highway Speeds

[Andrew Harvey]

How about your suggestion, assigning defaults based on urban/rural, which
you may be able to roughly assign based on buffering highway=residential?

Otherwise I think this will always be lacking in OSM until those maxspeed
tags are set.

In NSW we have some open data
https://opendata.transport.nsw.gov.au/dataset/speed-zones but the usual
issues about the accuracy of that data applies, but perhaps it could be
used to fill in the blanks?

On Tue, 19 Apr 2022 at 11:54, Andrew Hughes  wrote:

> Hi All,
>
> We're using OSM and pgrouting and it's GREAT!
>
> Something that I have found difficult to come to terms with, is assigning
> a "default speed" for unclassified roads (without a maxspeed tag). This is
> because in metro area's these are most-likely to be 50kph. However, out in
> regional areas these are likely to be 100kph.
>
> *Examples:*
>
> Unclassified Roads in Brisbane: Likely to be 50kph (default)
> https://overpass-turbo.eu/s/1hLK
>
> Unclassified Roads in Yorke Peninsula Council: Likely to be 100kph
> (default)
> https://overpass-turbo.eu/s/1hLL
>
> *Question:*
>
> What would be the best approach to achieving a more realistic speed given
> the above (while also taking into consideration the tagging guidelines)?
>
> Thanks in advance
> Andrew
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Re: [talk-au] Unclassified Highway Speeds

[stevea]

On Apr 18, 2022, at 6:50 PM, Andrew Hughes  wrote:
> We're using OSM and pgrouting and it's GREAT!
> 
> Something that I have found difficult to come to terms with, is assigning a 
> "default speed" for unclassified roads (without a maxspeed tag). This is 
> because in metro area's these are most-likely to be 50kph. However, out in 
> regional areas these are likely to be 100kph.

This is an interesting “edge” that OSM seems to bump up against every now and 
then, sometimes rather public (like on a talk-list), sometimes less so, but it 
still happens.

The following is a bit fuzzy, please allow me a bit of leeway.

What I have noticed is that there are “defaults” in a legal jurisdiction for an 
activity (such as “driving through a residential zone in the state of X”) where 
that implies 40 km/hr, or 25 MPH, or some such.  What OSM seems to continue to 
struggle to do is to somehow capture this idea, whether in tagging, in wiki, in 
“understood defaults” or in some combination of the above (and/or more inputs).

While it might seem like this can be done and/or is a good idea, it can break 
down as a wider audience (of OSM downstream users / renderers / routers / use 
cases) struggles to “parse what is.”  By the latter, what I mean is that the 
combination of ambiguously “understood to apply” defaults (whether legal, in 
OSM somehow, like in a wiki, or other) become murky.  It isn’t always clear 
what to do because of what is tagged (and what might be, or isn’t, or could be) 
and understood.

Please, I urge all to be careful when we make assumptions based on “well, in 
Western Australia…” (for example) because this is a commercial zone, we can 
assume a speed limit on an unclassified road.  Sometimes it’s safe / effective 
/ realistic to assume defaults apply, much of the time it is not, and such 
assumptions are folly.  It can be difficult to even describe these, as I 
struggle for words as I type here.

So, if you’re going to do this, you have to imagine that you can imagine all 
future, downstream use-cases.  Maybe you can, maybe you can’t.  Be careful.
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