[talk-au] maxspeed - best practice?

[Ben Johnson]

In regards to residential areas - I remember last year there was some  
talk about the bot that added "50" with the (incorrect)  
"maxspeed:source" key = "default residential speed limit in  
Australia"  and I think there was consensus in the local community  
that this was a mistake.


With remapping some of my local areas, I'm now curious what's best  
practice in Australia is for tagging maxspeed on residential streets.  
Specifically...


a) is it even necessary or desirable to explicitly define maxspeed for  
every residential way - or should we just presume any  
highway=residential is maxspeed=50, unless otherwise stated?


b) if presumptions do exist, should 50 zones on tertiary and  
unclassified ways be explictly tagged ?


c) if tagging maxspeed on every street, in respect to source... does a  
simple source:maxspeed=sign suffice for the "general area" or only for  
the specific way on which the sign is placed?  I notice these  
residential 50 speed signs are often on tertiary streets, or gateway  
points into general residential areas.  Side-streets obviously share  
the 50 limit, but are mostly not signposted. Do we need a new standard  
source value like source:maxspeed=implied for the side streets ?


Sorry if I'm re-covering old ground - I'm just not sure where it was  
left... if anywhere!


Thanks in advance.. BJ


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Re: [talk-au] maxspeed - best practice?

[Ian Sergeant]

Hi,

a) The thing is, if you don't tag maxspeed=50, then how do tell a
residential road that is known to be maxspeed=50, against one that is just
un-surveyed, and might be maxspeed=30,40 or 60?

c) source:maxspeed=sign is clearly correct if there is a sign. If you've
surveyed around an area, and there isn't a sign, personally I'd tag
source:maxspeed=survey.  The alternative here, would be
source:maxspeed=default or some such, but given our history of tagging
"site unseen".   It  I think this is best avoided. Same goes for
source=implied for the same reason.  If you've visited and determined the
speed limit, it is a survey.   maxspeed=local_knowledge if you drive around
the residential streets in your area all the time, and you just know they
are all 50km/h.

Just an aside,  a simple case study in presumptions.  Probably the most
popular OSM open source router is OSRM.  The speedprofiles for that project
you can see here

https://github.com/DennisOSRM/Project-OSRM/blob/master/speedprofile.ini

I believe OSRM will use a maxspeed on a street if it finds one, so once you
start marking maxspeeds it makes sense to mark others around them,
otherwise a maxspeed=40 road will become a preferred road over other
residentials and secondaries.

I'm sure the motivation for tagging all residentials as maxspeed=50 was
partly an attempt to address this issue.

Of course, there is a good argument for this being fixed in OSRM, or in
post-processing the AU data, etc.

Ian.

On 14 August 2012 15:30, Ben Johnson  wrote:

> In regards to residential areas - I remember last year there was some talk
> about the bot that added "50" with the (incorrect) "maxspeed:source" key =
> "default residential speed limit in Australia"  and I think there was
> consensus in the local community that this was a mistake.
>
> With remapping some of my local areas, I'm now curious what's best
> practice in Australia is for tagging maxspeed on residential streets.
> Specifically...
>
> a) is it even necessary or desirable to explicitly define maxspeed for
> every residential way - or should we just presume any highway=residential
> is maxspeed=50, unless otherwise stated?
>
> b) if presumptions do exist, should 50 zones on tertiary and unclassified
> ways be explictly tagged ?
>
> c) if tagging maxspeed on every street, in respect to source... does a
> simple source:maxspeed=sign suffice for the "general area" or only for the
> specific way on which the sign is placed?  I notice these residential 50
> speed signs are often on tertiary streets, or gateway points into general
> residential areas.  Side-streets obviously share the 50 limit, but are
> mostly not signposted. Do we need a new standard source value like
> source:maxspeed=implied for the side streets ?
>
> Sorry if I'm re-covering old ground - I'm just not sure where it was
> left... if anywhere!
>
> Thanks in advance.. BJ
>
>
> __**_
> Talk-au mailing list
> Talk-au@openstreetmap.org
> http://lists.openstreetmap.**org/listinfo/talk-au
>
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Re: [talk-au] Fixing relations in Canberra

[Nick Hocking]

Mark wrote "Can someone help with a couple of these in the ACT?"

Certainly can,  I'll drive them tonight and/or tomorrow morning and we'll
get them them sorted out.
>From memory the routes diverge near the circles and we have to take ALT  23
into account as well.

Cheers
Nick
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